diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Microsoft/AspNetCore/Razor/TagHelpers/AbpTagHelperAttributeListExtensions.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Microsoft/AspNetCore/Razor/TagHelpers/AbpTagHelperAttributeListExtensions.cs
index 81aefb7382..def91ef68b 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Microsoft/AspNetCore/Razor/TagHelpers/AbpTagHelperAttributeListExtensions.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Microsoft/AspNetCore/Razor/TagHelpers/AbpTagHelperAttributeListExtensions.cs
@@ -22,7 +22,7 @@ public static class AbpTagHelperAttributeListExtensions
         }
         else
         {
-            var existingClasses = classAttribute.Value.ToString().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
+            var existingClasses = classAttribute.Value.ToString()!.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
             existingClasses.AddIfNotContains(className);
             attributes.SetAttribute("class", string.Join(" ", existingClasses));
         }
@@ -41,7 +41,7 @@ public static class AbpTagHelperAttributeListExtensions
             return;
         }
 
-        var classList = classAttribute.Value.ToString().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
+        var classList = classAttribute.Value.ToString()!.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
         classList.RemoveAll(c => c == className);
 
         attributes.SetAttribute("class", classList.JoinAsString(" "));
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelper.cs
index 5b9c1430f2..8d0227fd11 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelper.cs
@@ -23,7 +23,7 @@ public abstract class AbpTagHelper<TTagHelper, TService> : AbpTagHelper
 
     [HtmlAttributeNotBound]
     [ViewContext]
-    public ViewContext ViewContext { get; set; }
+    public ViewContext ViewContext { get; set; } = default!;
 
     protected AbpTagHelper(TService service)
     {
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperLocalizer.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperLocalizer.cs
index c4314134be..5b6db4ff17 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperLocalizer.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperLocalizer.cs
@@ -27,12 +27,12 @@ public class AbpTagHelperLocalizer : IAbpTagHelperLocalizer
             : localizer[text].Value;
     }
 
-    public IStringLocalizer GetLocalizerOrNull(ModelExplorer explorer)
+    public IStringLocalizer? GetLocalizerOrNull(ModelExplorer explorer)
     {
         return GetLocalizerOrNull(explorer.Container.ModelType.Assembly);
     }
 
-    public IStringLocalizer GetLocalizerOrNull(Assembly assembly)
+    public IStringLocalizer? GetLocalizerOrNull(Assembly assembly)
     {
         var resourceType = GetResourceType(assembly);
         return resourceType == null
@@ -40,7 +40,7 @@ public class AbpTagHelperLocalizer : IAbpTagHelperLocalizer
             : _stringLocalizerFactory.Create(resourceType);
     }
 
-    private Type GetResourceType(Assembly assembly)
+    private Type? GetResourceType(Assembly assembly)
     {
         return _options
             .AssemblyResources
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperService.cs
index b9c3aa92e6..95de4f7f51 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/AbpTagHelperService.cs
@@ -23,7 +23,7 @@ public abstract class AbpTagHelperService<TTagHelper> : IAbpTagHelperService<TTa
     protected const string AbpTabItemSelectedPlaceholder = "{_Tab_Selected_Placeholder_}";
     protected const string AbpAccordionParentIdPlaceholder = "{_Parent_Accordion_Id_}";
 
-    public TTagHelper TagHelper { get; internal set; }
+    public TTagHelper TagHelper { get; internal set; } = default!;
 
     public virtual int Order { get; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/AbpBreadcrumbItemTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/AbpBreadcrumbItemTagHelper.cs
index 71ce3406fa..650b1efb0a 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/AbpBreadcrumbItemTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/AbpBreadcrumbItemTagHelper.cs
@@ -2,9 +2,9 @@
 
 public class AbpBreadcrumbItemTagHelper : AbpTagHelper<AbpBreadcrumbItemTagHelper, AbpBreadcrumbItemTagHelperService>
 {
-    public string Href { get; set; }
+    public string? Href { get; set; }
 
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
     public bool Active { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/BreadcrumbItem.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/BreadcrumbItem.cs
index 37a194b906..de9f59ca01 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/BreadcrumbItem.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Breadcrumb/BreadcrumbItem.cs
@@ -2,7 +2,7 @@
 
 public class BreadcrumbItem
 {
-    public string Html { get; set; }
+    public string Html { get; set; } = default!;
 
     public bool Active { get; set; }
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelper.cs
index 624d750274..60c986f34b 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelper.cs
@@ -9,11 +9,11 @@ public class AbpButtonTagHelper : AbpTagHelper<AbpButtonTagHelper, AbpButtonTagH
 
     public AbpButtonSize Size { get; set; } = AbpButtonSize.Default;
 
-    public string BusyText { get; set; }
+    public string? BusyText { get; set; }
 
-    public string Text { get; set; }
+    public string? Text { get; set; }
 
-    public string Icon { get; set; }
+    public string? Icon { get; set; }
 
     public bool? Disabled { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelperServiceBase.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelperServiceBase.cs
index 17422327c8..a69d09eed4 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelperServiceBase.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpButtonTagHelperServiceBase.cs
@@ -57,7 +57,7 @@ public abstract class AbpButtonTagHelperServiceBase<TTagHelper> : AbpTagHelperSe
             case FontIconType.FontAwesome:
                 return "fa fa-" + TagHelper.Icon;
             default:
-                return TagHelper.Icon;
+                return TagHelper.Icon!;
         }
     }
 
@@ -69,7 +69,7 @@ public abstract class AbpButtonTagHelperServiceBase<TTagHelper> : AbpTagHelperSe
         }
 
         var span = new TagBuilder("span");
-        span.InnerHtml.AppendHtml(TagHelper.Text);
+        span.InnerHtml.AppendHtml(TagHelper.Text!);
         output.Content.AppendHtml(span);
     }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpLinkButtonTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpLinkButtonTagHelper.cs
index bf3b4d8bac..53508864cd 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpLinkButtonTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/AbpLinkButtonTagHelper.cs
@@ -11,9 +11,9 @@ public class AbpLinkButtonTagHelper : AbpTagHelper<AbpLinkButtonTagHelper, AbpLi
 
     public AbpButtonSize Size { get; set; } = AbpButtonSize.Default;
 
-    public string Text { get; set; }
+    public string? Text { get; set; }
 
-    public string Icon { get; set; }
+    public string? Icon { get; set; }
 
     public bool? Disabled { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/IButtonTagHelperBase.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/IButtonTagHelperBase.cs
index 8ba73b2ab9..56e48c83de 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/IButtonTagHelperBase.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Button/IButtonTagHelperBase.cs
@@ -6,9 +6,9 @@ public interface IButtonTagHelperBase
 
     AbpButtonSize Size { get; }
 
-    string Text { get; }
+    string? Text { get; }
 
-    string Icon { get; }
+    string? Icon { get; }
 
     bool? Disabled { get; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelper.cs
index 34a14e6f33..c33293e13f 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelper.cs
@@ -2,9 +2,9 @@
 
 public class AbpCardBodyTagHelper : AbpTagHelper<AbpCardBodyTagHelper, AbpCardBodyTagHelperService>
 {
-    public string Title { get; set; }
+    public string? Title { get; set; }
 
-    public string Subtitle { get; set; }
+    public string? Subtitle { get; set; }
 
     public AbpCardBodyTagHelper(AbpCardBodyTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelperService.cs
index 172fa778b6..e50d0a791a 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Card/AbpCardBodyTagHelperService.cs
@@ -22,7 +22,7 @@ public class AbpCardBodyTagHelperService : AbpTagHelperService<AbpCardBodyTagHel
         {
             var cardTitle = new TagBuilder(AbpCardTitleTagHelper.DefaultHeading.ToHtmlTag());
             cardTitle.AddCssClass("card-title");
-            cardTitle.InnerHtml.AppendHtml(TagHelper.Title);
+            cardTitle.InnerHtml.AppendHtml(TagHelper.Title!);
             output.PreContent.AppendHtml(cardTitle);
         }
     }
@@ -33,7 +33,7 @@ public class AbpCardBodyTagHelperService : AbpTagHelperService<AbpCardBodyTagHel
         {
             var cardSubtitle = new TagBuilder(AbpCardSubtitleTagHelper.DefaultHeading.ToHtmlTag());
             cardSubtitle.AddCssClass("card-subtitle text-muted mb-2");
-            cardSubtitle.InnerHtml.AppendHtml(TagHelper.Subtitle);
+            cardSubtitle.InnerHtml.AppendHtml(TagHelper.Subtitle!);
             output.PreContent.AppendHtml(cardSubtitle);
         }
     }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelper.cs
index 65a47b73c4..3a1f82fb51 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelper.cs
@@ -4,13 +4,13 @@ public class AbpCarouselItemTagHelper : AbpTagHelper<AbpCarouselItemTagHelper, A
 {
     public bool? Active { get; set; }
 
-    public string Src { get; set; }
+    public string Src { get; set; } = default!;
 
-    public string Alt { get; set; }
+    public string Alt { get; set; } = default!;
 
-    public string CaptionTitle { get; set; }
+    public string? CaptionTitle { get; set; }
 
-    public string Caption { get; set; }
+    public string? Caption { get; set; }
 
     public AbpCarouselItemTagHelper(AbpCarouselItemTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelperService.cs
index a8a3030e95..370d781f04 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselItemTagHelperService.cs
@@ -66,10 +66,10 @@ public class AbpCarouselItemTagHelperService : AbpTagHelperService<AbpCarouselIt
         }
 
         var title = new TagBuilder("h5");
-        title.InnerHtml.AppendHtml(TagHelper.CaptionTitle);
+        title.InnerHtml.AppendHtml(TagHelper.CaptionTitle!);
 
         var caption = new TagBuilder("p");
-        caption.InnerHtml.AppendHtml(TagHelper.Caption);
+        caption.InnerHtml.AppendHtml(TagHelper.Caption!);
 
         var wrapper = new TagBuilder("div");
         wrapper.AddCssClass("carousel-caption d-none d-md-block");
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelper.cs
index e9931241c2..eb9cac08f1 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelper.cs
@@ -2,7 +2,7 @@
 
 public class AbpCarouselTagHelper : AbpTagHelper<AbpCarouselTagHelper, AbpCarouselTagHelperService>
 {
-    public string Id { get; set; }
+    public string? Id { get; set; }
 
     public bool? Crossfade { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelperService.cs
index 9264737b7b..af81b045f5 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Carousel/AbpCarouselTagHelperService.cs
@@ -138,7 +138,7 @@ public class AbpCarouselTagHelperService : AbpTagHelperService<AbpCarouselTagHel
     {
         if (!itemList.Any(it => it.Active) && itemList.Count > 0)
         {
-            itemList.FirstOrDefault().Active = true;
+            itemList.FirstOrDefault()!.Active = true;
         }
     }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionItemTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionItemTagHelper.cs
index 8742631e9a..99dd4ff3a1 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionItemTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionItemTagHelper.cs
@@ -2,9 +2,9 @@
 
 public class AbpAccordionItemTagHelper : AbpTagHelper<AbpAccordionItemTagHelper, AbpAccordionItemTagHelperService>
 {
-    public string Id { get; set; }
+    public string? Id { get; set; }
 
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
     public bool? Active { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionTagHelper.cs
index 49cca3199f..a4a87ab32a 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpAccordionTagHelper.cs
@@ -2,7 +2,7 @@
 
 public class AbpAccordionTagHelper : AbpTagHelper<AbpAccordionTagHelper, AbpAccordionTagHelperService>
 {
-    public string Id { get; set; }
+    public string? Id { get; set; }
 
     public AbpAccordionTagHelper(AbpAccordionTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseBodyTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseBodyTagHelper.cs
index cd6d5d43ed..477c8ed1d8 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseBodyTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseBodyTagHelper.cs
@@ -2,7 +2,7 @@
 
 public class AbpCollapseBodyTagHelper : AbpTagHelper<AbpCollapseBodyTagHelper, AbpCollapseBodyTagHelperService>
 {
-    public string Id { get; set; }
+    public string? Id { get; set; }
 
     public bool? Multi { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseButtonTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseButtonTagHelper.cs
index c1219b3bbb..64d90496c3 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseButtonTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Collapse/AbpCollapseButtonTagHelper.cs
@@ -8,7 +8,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Collapse;
 public class AbpCollapseButtonTagHelper : AbpTagHelper<AbpCollapseButtonTagHelper, AbpCollapseButtonTagHelperService>
 {
     [HtmlAttributeName("abp-collapse-id")]
-    public string BodyId { get; set; }
+    public string BodyId { get; set; } = default!;
 
     public AbpCollapseButtonTagHelper(AbpCollapseButtonTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Dropdown/AbpDropdownButtonTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Dropdown/AbpDropdownButtonTagHelper.cs
index ac87900307..bc0778cb47 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Dropdown/AbpDropdownButtonTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Dropdown/AbpDropdownButtonTagHelper.cs
@@ -4,7 +4,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Dropdown;
 
 public class AbpDropdownButtonTagHelper : AbpTagHelper<AbpDropdownButtonTagHelper, AbpDropdownButtonTagHelperService>
 {
-    public string Text { get; set; }
+    public string? Text { get; set; }
 
     public AbpButtonSize Size { get; set; } = AbpButtonSize.Default;
 
@@ -12,7 +12,7 @@ public class AbpDropdownButtonTagHelper : AbpTagHelper<AbpDropdownButtonTagHelpe
 
     public AbpButtonType ButtonType { get; set; } = AbpButtonType.Default;
 
-    public string Icon { get; set; }
+    public string? Icon { get; set; }
 
     public FontIconType IconType { get; set; } = FontIconType.FontAwesome;
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/ModelExplorerExtensions.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/ModelExplorerExtensions.cs
index eced70b75e..0e33d425e7 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/ModelExplorerExtensions.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/ModelExplorerExtensions.cs
@@ -7,9 +7,9 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Extensions;
 
 public static class ModelExplorerExtensions
 {
-    public static T GetAttribute<T>(this ModelExplorer property) where T : Attribute
+    public static T? GetAttribute<T>(this ModelExplorer property) where T : Attribute
     {
-        return property?.Metadata?.ContainerType?.GetTypeInfo()?.GetProperty(property.Metadata.PropertyName)?.GetCustomAttribute<T>();
+        return property?.Metadata?.ContainerType?.GetTypeInfo()?.GetProperty(property.Metadata.PropertyName!)?.GetCustomAttribute<T>();
     }
 
     public static int GetDisplayOrder(this ModelExplorer explorer)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/TagHelperContextExtensions.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/TagHelperContextExtensions.cs
index 47ab8827e7..bda437f8c5 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/TagHelperContextExtensions.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Extensions/TagHelperContextExtensions.cs
@@ -11,7 +11,7 @@ public static class TagHelperContextExtensions
     {
         if (!context.Items.ContainsKey(key))
         {
-            return default(T);
+            return default(T)!;
         }
 
         return (T)context.Items[key];
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelper.cs
index 6f2ed964cb..4e4b86a308 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelper.cs
@@ -12,7 +12,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form;
 public class AbpDynamicFormTagHelper : AbpTagHelper<AbpDynamicFormTagHelper, AbpDynamicFormTagHelperService>
 {
     [HtmlAttributeName("abp-model")]
-    public ModelExpression Model { get; set; }
+    public ModelExpression Model { get; set; } = default!;
 
     [HtmlAttributeName("column-size")]
     public ColumnSize ColumnSize { get; set; }
@@ -23,7 +23,7 @@ public class AbpDynamicFormTagHelper : AbpTagHelper<AbpDynamicFormTagHelper, Abp
 
     #region MvcFormTagHelperAttiributes
     
-    private IDictionary<string, string> _routeValues;
+    private IDictionary<string, string>? _routeValues;
 
     private const string ActionAttributeName = "asp-action";
     private const string AreaAttributeName = "asp-area";
@@ -36,28 +36,28 @@ public class AbpDynamicFormTagHelper : AbpTagHelper<AbpDynamicFormTagHelper, Abp
     private const string RouteValuesPrefix = "asp-route-";
 
     [HtmlAttributeName(ActionAttributeName)]
-    public string Action { get; set; }
+    public string Action { get; set; } = default!;
 
     [HtmlAttributeName(ControllerAttributeName)]
-    public string Controller { get; set; }
+    public string Controller { get; set; } = default!;
 
     [HtmlAttributeName(AreaAttributeName)]
-    public string Area { get; set; }
+    public string Area { get; set; } = default!;
 
     [HtmlAttributeName(PageAttributeName)]
-    public string Page { get; set; }
+    public string Page { get; set; } = default!;
 
     [HtmlAttributeName(PageHandlerAttributeName)]
-    public string PageHandler { get; set; }
+    public string PageHandler { get; set; } = default!;
 
     [HtmlAttributeName(FragmentAttributeName)]
-    public string Fragment { get; set; }
+    public string Fragment { get; set; } = default!;
 
     [HtmlAttributeName(RouteAttributeName)]
-    public string Route { get; set; }
+    public string Route { get; set; } = default!;
 
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public string Method { get; set; }
+    public string Method { get; set; } = default!;
 
     [HtmlAttributeName(RouteValuesDictionaryName, DictionaryAttributePrefix = RouteValuesPrefix)]
     public IDictionary<string, string> RouteValues
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelperService.cs
index 5938ad356d..57fa9fe0fb 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpDynamicformTagHelperService.cs
@@ -201,7 +201,7 @@ public class AbpDynamicFormTagHelperService : AbpTagHelperService<AbpDynamicForm
 
     private AbpTagHelper GetAbpDateRangeInputTagHelper(TagHelperContext context, TagHelperOutput output, ModelExpression model)
     {
-        var modelAttribute = model.ModelExplorer.GetAttribute<DateRangePickerAttribute>();
+        var modelAttribute = model.ModelExplorer.GetAttribute<DateRangePickerAttribute>()!;
 
         var pickerId = modelAttribute.PickerId;
 
@@ -214,16 +214,16 @@ public class AbpDynamicFormTagHelperService : AbpTagHelperService<AbpDynamicForm
             abpDateRangeInputTagHelper.AspForStart = model;
 
             var otherModelExists = TryToGetOtherDateModel(model, pickerId, out var otherModel);
-            if (otherModelExists && otherModel.GetAttribute<DateRangePickerAttribute>().IsEnd)
+            if (otherModelExists && otherModel!.GetAttribute<DateRangePickerAttribute>()!.IsEnd)
             {
-                abpDateRangeInputTagHelper.AspForEnd = ModelExplorerToModelExpressionConverter(otherModel);
+                abpDateRangeInputTagHelper.AspForEnd = ModelExplorerToModelExpressionConverter(otherModel!);
             }
         }
 
         return abpDateRangeInputTagHelper;
     }
 
-    private bool TryToGetOtherDateModel(ModelExpression model, string pickerId, out ModelExplorer otherModel)
+    private bool TryToGetOtherDateModel(ModelExpression model, string pickerId, out ModelExplorer? otherModel)
     {
         otherModel = TagHelper.Model.ModelExplorer.Properties.SingleOrDefault(x => x != model.ModelExplorer && x.GetAttribute<DateRangePickerAttribute>()?.PickerId == pickerId);
         return otherModel != null;
@@ -266,7 +266,7 @@ public class AbpDynamicFormTagHelperService : AbpTagHelperService<AbpDynamicForm
 
     protected virtual AbpTagHelper GetAbpRadioInputTagHelper(ModelExpression model)
     {
-        var radioButtonAttribute = model.ModelExplorer.GetAttribute<AbpRadioButton>();
+        var radioButtonAttribute = model.ModelExplorer.GetAttribute<AbpRadioButton>()!;
         var abpRadioInputTagHelper = _serviceProvider.GetRequiredService<AbpRadioInputTagHelper>();
         abpRadioInputTagHelper.AspFor = model;
         abpRadioInputTagHelper.AspItems = null;
@@ -356,7 +356,7 @@ public class AbpDynamicFormTagHelperService : AbpTagHelperService<AbpDynamicForm
         return type.ToString().StartsWith("System.Collections.Generic.IEnumerable`") || type.ToString().StartsWith("System.Collections.Generic.List`");
     }
 
-    protected virtual bool IsCsharpClassOrPrimitive(Type type)
+    protected virtual bool IsCsharpClassOrPrimitive(Type? type)
     {
         if (type == null)
         {
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpIdNameTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpIdNameTagHelper.cs
index d24e247abe..c83762a4a1 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpIdNameTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpIdNameTagHelper.cs
@@ -18,7 +18,7 @@ public class AbpIdNameTagHelper : AbpTagHelper
     public override int Order => -1000 - 1;
 
     [HtmlAttributeName("abp-id-name")]
-    public ModelExpression IdNameFor { get; set; }
+    public ModelExpression? IdNameFor { get; set; }
 
     private readonly MvcViewOptions _mvcViewOptions;
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelper.cs
index 8c58e3c285..a426b50d33 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelper.cs
@@ -6,11 +6,11 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form;
 
 public class AbpInputTagHelper : AbpTagHelper<AbpInputTagHelper, AbpInputTagHelperService>
 {
-    public ModelExpression AspFor { get; set; }
+    public ModelExpression AspFor { get; set; } = default!;
 
-    public string Label { get; set; }
+    public string? Label { get; set; }
 
-    public string LabelTooltip { get; set; }
+    public string? LabelTooltip { get; set; }
 
     public string LabelTooltipIcon { get; set; } = "bi-info-circle";
 
@@ -19,7 +19,7 @@ public class AbpInputTagHelper : AbpTagHelper<AbpInputTagHelper, AbpInputTagHelp
     public bool LabelTooltipHtml  { get; set; } = false;
 
     [HtmlAttributeName("info")]
-    public string InfoText { get; set; }
+    public string? InfoText { get; set; }
 
     [HtmlAttributeName("disabled")]
     public bool IsDisabled { get; set; } = false;
@@ -30,7 +30,7 @@ public class AbpInputTagHelper : AbpTagHelper<AbpInputTagHelper, AbpInputTagHelp
     public bool AutoFocus { get; set; }
 
     [HtmlAttributeName("type")]
-    public string InputTypeName { get; set; }
+    public string? InputTypeName { get; set; }
 
     public AbpFormControlSize Size { get; set; } = AbpFormControlSize.Default;
 
@@ -38,11 +38,11 @@ public class AbpInputTagHelper : AbpTagHelper<AbpInputTagHelper, AbpInputTagHelp
     public bool DisplayRequiredSymbol { get; set; } = true;
 
     [HtmlAttributeName("asp-format")]
-    public string Format { get; set; }
+    public string? Format { get; set; }
 
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
-    public string Value { get; set; }
+    public string? Value { get; set; }
 
     public bool SuppressLabel { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelperService.cs
index d3469c77bf..981116aa9f 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpInputTagHelperService.cs
@@ -397,7 +397,7 @@ public class AbpInputTagHelperService : AbpTagHelperService<AbpInputTagHelper>
         }
     }
 
-    protected virtual TextArea TryGetTextAreaAttribute(TagHelperOutput output)
+    protected virtual TextArea? TryGetTextAreaAttribute(TagHelperOutput output)
     {
         var textAreaAttribute = TagHelper.AspFor.ModelExplorer.GetAttribute<TextArea>();
 
@@ -479,14 +479,14 @@ public class AbpInputTagHelperService : AbpTagHelperService<AbpInputTagHelper>
 
     protected virtual bool IsOutputHidden(TagHelperOutput inputTag)
     {
-        return inputTag.Attributes.Any(a => a.Name.ToLowerInvariant() == "type" && a.Value.ToString().ToLowerInvariant() == "hidden");
+        return inputTag.Attributes.Any(a => a.Name.ToLowerInvariant() == "type" && a.Value.ToString()!.ToLowerInvariant() == "hidden");
     }
 
     protected virtual string GetIdAttributeValue(TagHelperOutput inputTag)
     {
         var idAttr = inputTag.Attributes.FirstOrDefault(a => a.Name == "id");
 
-        return idAttr != null ? idAttr.Value.ToString() : string.Empty;
+        return idAttr != null ? idAttr.Value.ToString()! : string.Empty;
     }
 
     protected virtual string GetIdAttributeAsString(TagHelperOutput inputTag)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelper.cs
index e076b13b04..0135d136ba 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelper.cs
@@ -8,15 +8,15 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form;
 [HtmlTargetElement("abp-radio")]
 public class AbpRadioInputTagHelper : AbpTagHelper<AbpRadioInputTagHelper, AbpRadioInputTagHelperService>
 {
-    public ModelExpression AspFor { get; set; }
+    public ModelExpression AspFor { get; set; } = default!;
 
-    public string Label { get; set; }
+    public string? Label { get; set; }
 
     public bool? Inline { get; set; }
 
     public bool? Disabled { get; set; }
 
-    public IEnumerable<SelectListItem> AspItems { get; set; }
+    public IEnumerable<SelectListItem>? AspItems { get; set; }
 
     public AbpRadioInputTagHelper(AbpRadioInputTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelperService.cs
index ea4bacb224..58e5300cbf 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpRadioInputTagHelperService.cs
@@ -113,12 +113,12 @@ public class AbpRadioInputTagHelperService : AbpTagHelperService<AbpRadioInputTa
         var localizer = _tagHelperLocalizer.GetLocalizerOrNull(explorer);
 
         var selectItems = explorer.Metadata.IsEnum ? explorer.ModelType.GetTypeInfo().GetMembers(BindingFlags.Public | BindingFlags.Static)
-            .Select((t, i) => new SelectListItem { Value = i.ToString(), Text = GetLocalizedPropertyName(localizer, explorer.ModelType, t.Name) }).ToList() : null;
+            .Select((t, i) => new SelectListItem { Value = i.ToString(), Text = GetLocalizedPropertyName(localizer, explorer.ModelType, t.Name) }).ToList() : new List<SelectListItem>();
 
         return selectItems;
     }
 
-    protected virtual string GetLocalizedPropertyName(IStringLocalizer localizer, Type enumType, string propertyName)
+    protected virtual string GetLocalizedPropertyName(IStringLocalizer? localizer, Type enumType, string propertyName)
     {
         if (localizer == null)
         {
@@ -159,7 +159,7 @@ public class AbpRadioInputTagHelperService : AbpTagHelperService<AbpRadioInputTa
         }
     }
 
-    protected virtual string GetSelectedValue(TagHelperContext context, TagHelperOutput output)
+    protected virtual string? GetSelectedValue(TagHelperContext context, TagHelperOutput output)
     {
         if (TagHelper.AspFor.ModelExplorer.Metadata.IsEnum)
         {
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelper.cs
index fd4c42fcff..7d11f69636 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelper.cs
@@ -8,41 +8,41 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form;
 [OutputElementHint("select")]
 public class AbpSelectTagHelper : AbpTagHelper<AbpSelectTagHelper, AbpSelectTagHelperService>
 {
-    public ModelExpression AspFor { get; set; }
+    public ModelExpression AspFor { get; set; } = default!;
 
-    public string Label { get; set; }
+    public string? Label { get; set; }
 
     public bool SuppressLabel { get; set; }
 
-    public IEnumerable<SelectListItem> AspItems { get; set; }
+    public IEnumerable<SelectListItem>? AspItems { get; set; }
 
     public AbpFormControlSize Size { get; set; } = AbpFormControlSize.Default;
 
     [HtmlAttributeName("info")]
-    public string InfoText { get; set; }
+    public string? InfoText { get; set; }
 
     [HtmlAttributeName("required-symbol")]
     public bool DisplayRequiredSymbol { get; set; } = true;
 
-    public string AutocompleteApiUrl { get; set; }
+    public string? AutocompleteApiUrl { get; set; }
 
-    public string AutocompleteItemsPropertyName { get; set; }
+    public string? AutocompleteItemsPropertyName { get; set; }
 
-    public string AutocompleteDisplayPropertyName { get; set; }
+    public string? AutocompleteDisplayPropertyName { get; set; }
 
-    public string AutocompleteValuePropertyName { get; set; }
+    public string? AutocompleteValuePropertyName { get; set; }
 
-    public string AutocompleteFilterParamName { get; set; }
+    public string? AutocompleteFilterParamName { get; set; }
 
-    public string AutocompleteSelectedItemName { get; set; }
+    public string? AutocompleteSelectedItemName { get; set; }
 
-    public string AutocompleteSelectedItemValue { get; set; }
+    public string? AutocompleteSelectedItemValue { get; set; }
     
-    public string AutocompleteParentSelector { get; set; }
+    public string? AutocompleteParentSelector { get; set; }
 
-    public string AllowClear { get; set; }
+    public string? AllowClear { get; set; }
 
-    public string Placeholder { get; set; }
+    public string? Placeholder { get; set; }
 
     [HtmlAttributeName("floating-label")]
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelperService.cs
index 90268b7429..0edc8f1008 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/AbpSelectTagHelperService.cs
@@ -266,7 +266,7 @@ public class AbpSelectTagHelperService : AbpTagHelperService<AbpSelectTagHelper>
 
         if (isNullableType)
         {
-            enumType = Nullable.GetUnderlyingType(explorer.ModelType);
+            enumType = Nullable.GetUnderlyingType(explorer.ModelType)!;
             selectItems.Add(new SelectListItem());
         }
 
@@ -279,7 +279,7 @@ public class AbpSelectTagHelperService : AbpTagHelperService<AbpSelectTagHelper>
                 {
                     containerLocalizer,
                     _stringLocalizerFactory.CreateDefaultOrNull()
-                });
+                }!);
             selectItems.Add(new SelectListItem
             {
                 Value = enumValue.ToString(),
@@ -386,7 +386,7 @@ public class AbpSelectTagHelperService : AbpTagHelperService<AbpSelectTagHelper>
     {
         var idAttr = inputTag.Attributes.FirstOrDefault(a => a.Name == "id");
 
-        return idAttr != null ? idAttr.Value.ToString() : string.Empty;
+        return idAttr != null ? idAttr.Value.ToString()! : string.Empty;
     }
 
     protected virtual string GetIdAttributeAsString(TagHelperOutput inputTag)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelper.cs
index 7f9c34fb7a..fed2981613 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelper.cs
@@ -11,9 +11,9 @@ public abstract class
 {
     private IAbpDatePickerOptions _abpDatePickerOptionsImplementation;
 
-    public string Label { get; set; }
+    public string? Label { get; set; }
 
-    public string LabelTooltip { get; set; }
+    public string? LabelTooltip { get; set; }
 
     public string LabelTooltipIcon { get; set; } = "bi-info-circle";
 
@@ -22,7 +22,7 @@ public abstract class
     public bool LabelTooltipHtml { get; set; } = false;
 
     [HtmlAttributeName("info")] 
-    public string InfoText { get; set; }
+    public string? InfoText { get; set; }
 
     [HtmlAttributeName("disabled")] 
     public bool IsDisabled { get; set; } = false;
@@ -37,9 +37,9 @@ public abstract class
     [HtmlAttributeName("required-symbol")] 
     public bool DisplayRequiredSymbol { get; set; } = true;
 
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
-    public string Value { get; set; }
+    public string? Value { get; set; }
 
     public bool SuppressLabel { get; set; }
 
@@ -53,7 +53,7 @@ public abstract class
         _abpDatePickerOptionsImplementation = options;
     }
 
-    public string PickerId {
+    public string? PickerId {
         get => _abpDatePickerOptionsImplementation.PickerId;
         set => _abpDatePickerOptionsImplementation.PickerId = value;
     }
@@ -68,7 +68,7 @@ public abstract class
         set => _abpDatePickerOptionsImplementation.MaxDate = value;
     }
 
-    public object MaxSpan {
+    public object? MaxSpan {
         get => _abpDatePickerOptionsImplementation.MaxSpan;
         set => _abpDatePickerOptionsImplementation.MaxSpan = value;
     }
@@ -113,7 +113,7 @@ public abstract class
         set => _abpDatePickerOptionsImplementation.TimePickerSeconds = value;
     }
 
-    public List<AbpDatePickerRange> Ranges {
+    public List<AbpDatePickerRange>? Ranges {
         get => _abpDatePickerOptionsImplementation.Ranges;
         set => _abpDatePickerOptionsImplementation.Ranges = value;
     }
@@ -138,27 +138,27 @@ public abstract class
         set => _abpDatePickerOptionsImplementation.Drops = value;
     }
 
-    public string ButtonClasses {
+    public string? ButtonClasses {
         get => _abpDatePickerOptionsImplementation.ButtonClasses;
         set => _abpDatePickerOptionsImplementation.ButtonClasses = value;
     }
 
-    public string TodayButtonClasses {
+    public string? TodayButtonClasses {
         get => _abpDatePickerOptionsImplementation.TodayButtonClasses;
         set => _abpDatePickerOptionsImplementation.TodayButtonClasses = value;
     }
 
-    public string ApplyButtonClasses {
+    public string? ApplyButtonClasses {
         get => _abpDatePickerOptionsImplementation.ApplyButtonClasses;
         set => _abpDatePickerOptionsImplementation.ApplyButtonClasses = value;
     }
 
-    public string ClearButtonClasses {
+    public string? ClearButtonClasses {
         get => _abpDatePickerOptionsImplementation.ClearButtonClasses;
         set => _abpDatePickerOptionsImplementation.ClearButtonClasses = value;
     }
 
-    public object Locale {
+    public object? Locale {
         get => _abpDatePickerOptionsImplementation.Locale;
         set => _abpDatePickerOptionsImplementation.Locale = value;
     }
@@ -178,12 +178,12 @@ public abstract class
         set => _abpDatePickerOptionsImplementation.AutoUpdateInput = value;
     }
 
-    public string ParentEl {
+    public string? ParentEl {
         get => _abpDatePickerOptionsImplementation.ParentEl;
         set => _abpDatePickerOptionsImplementation.ParentEl = value;
     }
 
-    public string DateFormat {
+    public string? DateFormat {
         get => _abpDatePickerOptionsImplementation.DateFormat;
         set => _abpDatePickerOptionsImplementation.DateFormat = value;
     }
@@ -213,7 +213,7 @@ public abstract class
         set => _abpDatePickerOptionsImplementation.IsIso = value;
     }
 
-    public object Options {
+    public object? Options {
         get => _abpDatePickerOptionsImplementation.Options;
         set => _abpDatePickerOptionsImplementation.Options = value;
     }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelperService.cs
index 92bb48b974..024fd4dd45 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerBaseTagHelperService.cs
@@ -46,7 +46,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
                 return string.Empty;
             }
         },
-        {typeof(DateTime?), o => ((DateTime?) o)?.ToString("O")},
+        {typeof(DateTime?), o => ((DateTime?) o)?.ToString("O")!},
         {
             typeof(DateTimeOffset), o =>
             {
@@ -58,7 +58,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
                 return string.Empty;
             }
         },
-        {typeof(DateTimeOffset?), o => ((DateTimeOffset?) o)?.ToString("O")}
+        {typeof(DateTimeOffset?), o => ((DateTimeOffset?) o)?.ToString("O")!}
     };
 
     protected readonly IJsonSerializer JsonSerializer;
@@ -85,12 +85,12 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         InputTagHelper = new InputTagHelper(Generator) { InputTypeName = "text" };
     }
 
-    protected virtual T GetAttribute<T>() where T : Attribute
+    protected virtual T? GetAttribute<T>() where T : Attribute
     {
         return GetAttributeAndModelExpression<T>(out _);
     }
 
-    protected abstract T GetAttributeAndModelExpression<T>(out ModelExpression modelExpression) where T : Attribute;
+    protected abstract T? GetAttributeAndModelExpression<T>(out ModelExpression? modelExpression) where T : Attribute;
 
 
     public async override Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
@@ -118,7 +118,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         var optionsAttribute = GetAttributeAndModelExpression<DatePickerOptionsAttribute>(out var modelExpression);
         if (optionsAttribute != null)
         {
-            TagHelper.SetDatePickerOptions(optionsAttribute.GetDatePickerOptions(modelExpression.ModelExplorer));
+            TagHelper.SetDatePickerOptions(optionsAttribute.GetDatePickerOptions(modelExpression!.ModelExplorer)!);
         }
 
         // Open and close button
@@ -250,7 +250,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         return string.Empty;
     }
 
-    protected TagHelperAttributeList ConvertDatePickerOptionsToAttributeList(IAbpDatePickerOptions options)
+    protected TagHelperAttributeList ConvertDatePickerOptionsToAttributeList(IAbpDatePickerOptions? options)
     {
         var attrList = new TagHelperAttributeList();
 
@@ -281,7 +281,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (options.ShowDropdowns == false)
         {
-            attrList.Add("data-show-dropdowns", options.ShowDropdowns.ToString().ToLowerInvariant());
+            attrList.Add("data-show-dropdowns", options.ShowDropdowns.ToString()!.ToLowerInvariant());
         }
 
         if (options.MinYear != null)
@@ -306,7 +306,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (options.TimePicker != null)
         {
-            attrList.Add("data-time-picker", options.TimePicker.ToString().ToLowerInvariant());
+            attrList.Add("data-time-picker", options.TimePicker.ToString()!.ToLowerInvariant());
         }
 
         if (options.TimePickerIncrement != null)
@@ -316,12 +316,12 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (options.TimePicker24Hour != null)
         {
-            attrList.Add("data-time-picker24-hour", options.TimePicker24Hour.ToString().ToLowerInvariant());
+            attrList.Add("data-time-picker24-hour", options.TimePicker24Hour.ToString()!.ToLowerInvariant());
         }
 
         if (options.TimePickerSeconds != null)
         {
-            attrList.Add("data-time-picker-seconds", options.TimePickerSeconds.ToString().ToLowerInvariant());
+            attrList.Add("data-time-picker-seconds", options.TimePickerSeconds.ToString()!.ToLowerInvariant());
         }
 
         if (options.Opens != AbpDatePickerOpens.Center)
@@ -356,17 +356,17 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (options.AutoApply != null)
         {
-            attrList.Add("data-auto-apply", options.AutoApply.ToString().ToLowerInvariant());
+            attrList.Add("data-auto-apply", options.AutoApply.ToString()!.ToLowerInvariant());
         }
 
         if (options.LinkedCalendars != null)
         {
-            attrList.Add("data-linked-calendars", options.LinkedCalendars.ToString().ToLowerInvariant());
+            attrList.Add("data-linked-calendars", options.LinkedCalendars.ToString()!.ToLowerInvariant());
         }
 
         if (options.AutoUpdateInput != null)
         {
-            attrList.Add("data-auto-update-input", options.AutoUpdateInput.ToString().ToLowerInvariant());
+            attrList.Add("data-auto-update-input", options.AutoUpdateInput.ToString()!.ToLowerInvariant());
         }
 
         if (!options.ParentEl.IsNullOrEmpty())
@@ -388,12 +388,12 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if(options.AlwaysShowCalendars != null)
         {
-            attrList.Add("data-always-show-calendars", options.AlwaysShowCalendars.ToString().ToLowerInvariant());
+            attrList.Add("data-always-show-calendars", options.AlwaysShowCalendars.ToString()!.ToLowerInvariant());
         }
 
         if(options.ShowCustomRangeLabel == false)
         {
-            attrList.Add("data-show-custom-range-label", options.ShowCustomRangeLabel.ToString().ToLowerInvariant());
+            attrList.Add("data-show-custom-range-label", options.ShowCustomRangeLabel.ToString()!.ToLowerInvariant());
         }
 
         if(options.Options != null)
@@ -403,12 +403,12 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (options.IsUtc != null)
         {
-            attrList.Add("data-is-utc", options.IsUtc.ToString().ToLowerInvariant());
+            attrList.Add("data-is-utc", options.IsUtc.ToString()!.ToLowerInvariant());
         }
 
         if (options.IsIso != null)
         {
-            attrList.Add("data-is-iso", options.IsIso.ToString().ToLowerInvariant());
+            attrList.Add("data-is-iso", options.IsIso.ToString()!.ToLowerInvariant());
         }
 
         if (!options.PickerId.IsNullOrWhiteSpace())
@@ -481,7 +481,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         }
 
         string text;
-        ModelExplorer modelExplorer = null;
+        ModelExplorer? modelExplorer = null;
 
         if (!string.IsNullOrEmpty(TagHelper.InfoText))
         {
@@ -492,7 +492,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
             var infoAttribute = GetAttributeAndModelExpression<InputInfoText>(out var modelExpression);
             if (infoAttribute != null)
             {
-                modelExplorer = modelExpression.ModelExplorer;
+                modelExplorer = modelExpression!.ModelExplorer;
                 text = infoAttribute.Text;
             }
             else
@@ -502,7 +502,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         }
 
         var idAttr = inputTag.Attributes.FirstOrDefault(a => a.Name == "id");
-        modelExplorer ??= GetModelExpression().ModelExplorer;
+        modelExplorer ??= GetModelExpression()!.ModelExplorer;
         var localizedText = TagHelperLocalizer.GetLocalizedText(text, modelExplorer);
 
         var div = new TagBuilder("div");
@@ -553,7 +553,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
     {
         var idAttr = inputTag.Attributes.FirstOrDefault(a => a.Name == "id");
 
-        return idAttr != null ? idAttr.Value.ToString() : string.Empty;
+        return idAttr != null ? idAttr.Value.ToString()! : string.Empty;
     }
 
     protected virtual string GetRequiredSymbol(TagHelperContext context, TagHelperOutput output)
@@ -568,7 +568,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         return GetAttribute<RequiredAttribute>() != null || isHaveRequiredAttribute ? "<span> * </span>" : "";
     }
 
-    protected abstract ModelExpression GetModelExpression();
+    protected abstract ModelExpression? GetModelExpression();
 
     protected virtual async Task<string> GetLabelAsHtmlUsingTagHelperAsync(TagHelperContext context,
         TagHelperOutput output)
@@ -651,7 +651,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
 
         if (infoAttribute != null)
         {
-            return TagHelperLocalizer.GetLocalizedText(infoAttribute.Text, modelExpression.ModelExplorer);
+            return TagHelperLocalizer.GetLocalizedText(infoAttribute.Text, modelExpression!.ModelExplorer);
         }
 
         return string.Empty;
@@ -669,7 +669,7 @@ public abstract class AbpDatePickerBaseTagHelperService<TTagHelper> : AbpTagHelp
         if (attribute != null)
         {
             var placeholderLocalized =
-                TagHelperLocalizer.GetLocalizedText(attribute.Value, modelExpression.ModelExplorer);
+                TagHelperLocalizer.GetLocalizedText(attribute.Value, modelExpression!.ModelExplorer);
 
             inputTagHelperOutput.Attributes.Add("placeholder", placeholderLocalized);
         }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerOptions.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerOptions.cs
index 15b4e2003d..2007a8a669 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerOptions.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerOptions.cs
@@ -5,10 +5,10 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form.DatePicker;
 
 public class AbpDatePickerOptions : IAbpDatePickerOptions
 {
-    public string PickerId { get; set; }
+    public string? PickerId { get; set; }
     public DateTime? MinDate { get; set; }
     public DateTime? MaxDate { get; set; }
-    public object MaxSpan { get; set; }
+    public object? MaxSpan { get; set; }
     public bool? ShowDropdowns { get; set; }
     public int? MinYear { get; set; }
     public int? MaxYear { get; set; }
@@ -17,25 +17,25 @@ public class AbpDatePickerOptions : IAbpDatePickerOptions
     public int? TimePickerIncrement { get; set; }
     public bool? TimePicker24Hour { get; set; }
     public bool? TimePickerSeconds { get; set; }
-    public List<AbpDatePickerRange> Ranges { get; set; }
+    public List<AbpDatePickerRange>? Ranges { get; set; }
     public bool? ShowCustomRangeLabel { get; set; }
     public bool? AlwaysShowCalendars { get; set; }
     public AbpDatePickerOpens Opens { get; set; } = AbpDatePickerOpens.Center;
     public AbpDatePickerDrops Drops { get; set; } = AbpDatePickerDrops.Down;
-    public string ButtonClasses { get; set; }
-    public string TodayButtonClasses { get; set; }
-    public string ApplyButtonClasses { get; set; }
-    public string ClearButtonClasses { get; set; }
-    public object Locale { get; set; }
+    public string? ButtonClasses { get; set; }
+    public string? TodayButtonClasses { get; set; }
+    public string? ApplyButtonClasses { get; set; }
+    public string? ClearButtonClasses { get; set; }
+    public object? Locale { get; set; }
     public bool? AutoApply { get; set; }
     public bool? LinkedCalendars { get; set; }
     public bool? AutoUpdateInput { get; set; }
-    public string ParentEl { get; set; }
-    public string DateFormat { get; set; }
+    public string? ParentEl { get; set; }
+    public string? DateFormat { get; set; }
     public bool OpenButton { get; set; } = true;
     public bool ClearButton { get; set; } = true;
     public bool SingleOpenAndClearButton { get; set; } = true;
     public bool? IsUtc { get; set; }
     public bool? IsIso { get; set; }
-    public object Options { get; set; }
+    public object? Options { get; set; }
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerRange.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerRange.cs
index eea3d2ad31..3dfee14018 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerRange.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerRange.cs
@@ -6,7 +6,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form.DatePicker;
 public class AbpDatePickerRange
 {
     private readonly List<string> _dates = new List<string>();
-    public string Label { get; set; }
+    public string Label { get; set; } = default!;
     public IReadOnlyList<string> Dates => _dates;
 
     public AbpDatePickerRange()
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelper.cs
index 8426b0071b..519952d21e 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelper.cs
@@ -7,8 +7,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form.DatePicker;
 [HtmlTargetElement("abp-date-picker", TagStructure = TagStructure.NormalOrSelfClosing)]
 public class AbpDatePickerTagHelper : AbpDatePickerBaseTagHelper<AbpDatePickerTagHelper>
 {
-    [CanBeNull] 
-    public ModelExpression AspFor { get; set; }
+    public ModelExpression? AspFor { get; set; }
     
     public AbpDatePickerTagHelper(AbpDatePickerTagHelperService service) : base(service)
     {
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelperService.cs
index 727ab1a239..d135d28667 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDatePickerTagHelperService.cs
@@ -19,19 +19,17 @@ public class AbpDatePickerTagHelperService : AbpDatePickerBaseTagHelperService<A
 
     }
 
-    protected override TagHelperOutput TagHelperOutput { get; set; }
+    protected override TagHelperOutput TagHelperOutput { get; set; } = default!;
 
-    [CanBeNull]
-    protected virtual InputTagHelper DateTagHelper { get; set; }
+    protected virtual InputTagHelper? DateTagHelper { get; set; }
 
-    [CanBeNull]
-    protected virtual TagHelperOutput DateTagHelperOutput { get; set; }
+    protected virtual TagHelperOutput? DateTagHelperOutput { get; set; }
     protected override string GetPropertyName()
     {
         return TagHelper.AspFor?.Name ?? string.Empty;
     }
 
-    protected override T GetAttributeAndModelExpression<T>(out ModelExpression modelExpression)
+    protected override T? GetAttributeAndModelExpression<T>(out ModelExpression? modelExpression) where T : class
     {
         modelExpression = TagHelper.AspFor;
         return modelExpression?.ModelExplorer.GetAttribute<T>();
@@ -74,7 +72,7 @@ public class AbpDatePickerTagHelperService : AbpDatePickerBaseTagHelperService<A
         }
     }
 
-    protected override ModelExpression GetModelExpression()
+    protected override ModelExpression? GetModelExpression()
     {
         return TagHelper.AspFor;
     }
@@ -86,6 +84,6 @@ public class AbpDatePickerTagHelperService : AbpDatePickerBaseTagHelperService<A
 
     protected override string GetExtraInputHtml(TagHelperContext context, TagHelperOutput output)
     {
-        return DateTagHelperOutput?.Render(Encoder);
+        return DateTagHelperOutput?.Render(Encoder)!;
     }
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelper.cs
index bfd1e354f6..e2f249bf28 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelper.cs
@@ -7,11 +7,9 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form.DatePicker;
 [HtmlTargetElement("abp-date-range-picker", TagStructure = TagStructure.NormalOrSelfClosing)]
 public class AbpDateRangePickerTagHelper : AbpDatePickerBaseTagHelper<AbpDateRangePickerTagHelper>
 {
-    [CanBeNull] 
-    public ModelExpression AspForStart { get; set; }
+    public ModelExpression? AspForStart { get; set; }
 
-    [CanBeNull] 
-    public ModelExpression AspForEnd { get; set; }
+    public ModelExpression? AspForEnd { get; set; }
 
     public AbpDateRangePickerTagHelper(AbpDateRangePickerTagHelperService tagHelperService) :
         base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelperService.cs
index 45a083b789..48eeb5ba94 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/AbpDateRangePickerTagHelperService.cs
@@ -25,7 +25,7 @@ public class AbpDateRangePickerTagHelperService : AbpDatePickerBaseTagHelperServ
 
     protected override string TagName { get; set; } = "abp-date-range-picker";
 
-    protected override T GetAttributeAndModelExpression<T>(out ModelExpression modelExpression)
+    protected override T? GetAttributeAndModelExpression<T>(out ModelExpression? modelExpression) where T : class
     {
         modelExpression = new[] { TagHelper.AspForStart, TagHelper.AspForEnd }.FirstOrDefault(x => x?.ModelExplorer?.GetAttribute<T>() != null);
         return modelExpression?.ModelExplorer.GetAttribute<T>();
@@ -62,19 +62,15 @@ public class AbpDateRangePickerTagHelperService : AbpDatePickerBaseTagHelperServ
         await base.ProcessAsync(context, output);
     }
 
-    protected override TagHelperOutput TagHelperOutput { get; set; }
+    protected override TagHelperOutput TagHelperOutput { get; set; } = default!;
 
-    [CanBeNull]
-    protected virtual InputTagHelper StartDateTagHelper { get; set; }
+    protected virtual InputTagHelper? StartDateTagHelper { get; set; }
 
-    [CanBeNull]
-    protected virtual TagHelperOutput StartDateTagHelperOutput { get; set; }
+    protected virtual TagHelperOutput? StartDateTagHelperOutput { get; set; }
 
-    [CanBeNull]
-    protected virtual InputTagHelper EndDateTagHelper { get; set; }
+    protected virtual InputTagHelper? EndDateTagHelper { get; set; }
 
-    [CanBeNull]
-    protected virtual TagHelperOutput EndDateTagHelperOutput { get; set; }
+    protected virtual TagHelperOutput? EndDateTagHelperOutput { get; set; }
 
     protected override string GetPropertyName()
     {
@@ -108,7 +104,7 @@ public class AbpDateRangePickerTagHelperService : AbpDatePickerBaseTagHelperServ
         return StartDateTagHelperOutput?.Render(Encoder) + EndDateTagHelperOutput?.Render(Encoder);
     }
 
-    protected override ModelExpression GetModelExpression()
+    protected override ModelExpression? GetModelExpression()
     {
         return TagHelper.AspForStart;
     }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/DatePickerOptionsAttribute.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/DatePickerOptionsAttribute.cs
index 9cff72aa23..235801bd78 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/DatePickerOptionsAttribute.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/DatePickerOptionsAttribute.cs
@@ -14,7 +14,7 @@ public class DatePickerOptionsAttribute : Attribute
         DatePickerOptionsPropertyName = datePickerOptionsPropertyName;
     }
     
-    public IAbpDatePickerOptions GetDatePickerOptions(ModelExplorer explorer)
+    public IAbpDatePickerOptions? GetDatePickerOptions(ModelExplorer explorer)
     {
         var properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName != null && p.Metadata.PropertyName.Equals(DatePickerOptionsPropertyName)).ToList();
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/IAbpDatePickerOptions.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/IAbpDatePickerOptions.cs
index 118c409da9..5244a844fa 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/IAbpDatePickerOptions.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/DatePicker/IAbpDatePickerOptions.cs
@@ -6,7 +6,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Form.DatePicker;
 
 public interface IAbpDatePickerOptions
 {
-    public string PickerId { get; set; }
+    public string? PickerId { get; set; }
 
     /// <summary>
     /// Min date allowed
@@ -21,7 +21,7 @@ public interface IAbpDatePickerOptions
     /// <summary>
     /// The maximum span between the selected start and end dates. Can have any property you can add to a moment object (i.e. days, months)
     /// </summary>
-    object MaxSpan { get; set; }
+    object? MaxSpan { get; set; }
 
     /// <summary>
     /// Show year and month select boxes above calendars to jump to a specific month and year.
@@ -66,7 +66,7 @@ public interface IAbpDatePickerOptions
     /// <summary>
     /// Set predefined date ranges the user can select from. Each key is the label for the range, and its value an array with two dates representing the bounds of the range.
     /// </summary>
-    List<AbpDatePickerRange> Ranges { get; set; }
+    List<AbpDatePickerRange>? Ranges { get; set; }
 
     /// <summary>
     /// Displays "Custom Range" at the end of the list of predefined ranges, when the ranges option is used. This option will be highlighted whenever the current date range selection does not match one of the predefined ranges. Clicking it will display the calendars to select a new range.
@@ -91,32 +91,28 @@ public interface IAbpDatePickerOptions
     /// <summary>
     /// CSS class names that will be added to both the today, clear, and apply buttons.
     /// </summary>
-    [CanBeNull]
-    string ButtonClasses { get; set; }
+    string? ButtonClasses { get; set; }
 
     /// <summary>
     /// CSS class names that will be added only to the today button.
     /// </summary>
-    [CanBeNull]
-    string TodayButtonClasses { get; set; }
+    string? TodayButtonClasses { get; set; }
     
     /// <summary>
     /// CSS class names that will be added only to the apply button.
     /// </summary>
-    [CanBeNull]
-    string ApplyButtonClasses { get; set; }
+    string? ApplyButtonClasses { get; set; }
 
     /// <summary>
     /// CSS class names that will be added only to the clear button.
     /// </summary>
-    [CanBeNull]
-    string ClearButtonClasses { get; set; }
+    string? ClearButtonClasses { get; set; }
 
     /// <summary>
     /// Allows you to provide localized strings for buttons and labels, customize the date format, and change the first day of week for the calendars.
     /// </summary>
     [CanBeNull]
-    object Locale { get; set; }
+    object? Locale { get; set; }
 
     /// <summary>
     /// Hide the apply button, and automatically apply a new date range as soon as two dates are clicked.
@@ -136,11 +132,9 @@ public interface IAbpDatePickerOptions
     /// <summary>
     /// jQuery selector of the parent element that the date range picker will be added to, if not provided this will be 'body'
     /// </summary>
-    [CanBeNull]
-    string ParentEl { get; set; }
+    string? ParentEl { get; set; }
     
-    [CanBeNull]
-    string DateFormat { get; set; }
+    string? DateFormat { get; set; }
 
     bool OpenButton { get; set; }
 
@@ -155,6 +149,5 @@ public interface IAbpDatePickerOptions
     /// <summary>
     /// Other non-mapped attributes will be automatically added to the input element as is.
     /// </summary>
-    [CanBeNull]
-    object Options { get; set; }
+    object? Options { get; set; }
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/FormGroupItem.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/FormGroupItem.cs
index b56d68abdf..82b82d50ac 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/FormGroupItem.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/FormGroupItem.cs
@@ -2,9 +2,9 @@
 
 public class FormGroupItem
 {
-    public string HtmlContent { get; set; }
+    public string HtmlContent { get; set; } = default!;
 
     public int Order { get; set; }
 
-    public string PropertyName { get; set; }
+    public string PropertyName { get; set; } = default!;
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/SelectItems.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/SelectItems.cs
index fc64858a56..7f9e530eb4 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/SelectItems.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Form/SelectItems.cs
@@ -16,9 +16,9 @@ public class SelectItems : Attribute
         ItemsListPropertyName = itemsListPropertyName;
     }
 
-    public IEnumerable<SelectListItem> GetItems(ModelExplorer explorer)
+    public IEnumerable<SelectListItem>? GetItems(ModelExplorer explorer)
     {
-        var properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName.Equals(ItemsListPropertyName)).ToList();
+        var properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName!.Equals(ItemsListPropertyName)).ToList();
 
         while (properties.Count == 0)
         {
@@ -28,10 +28,10 @@ public class SelectItems : Attribute
                 return null;
             }
 
-            properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName.Equals(ItemsListPropertyName)).ToList();
+            properties = explorer.Container.Properties.Where(p => p.Metadata.PropertyName!.Equals(ItemsListPropertyName)).ToList();
         }
 
-        var selectItems = (properties.First().Model as IEnumerable<SelectListItem>).ToList();
+        var selectItems = (properties.First().Model as IEnumerable<SelectListItem>)!.ToList();
 
         return selectItems;
     }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/IAbpTagHelperLocalizer.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/IAbpTagHelperLocalizer.cs
index ca3ae84de3..f19f1dd8d7 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/IAbpTagHelperLocalizer.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/IAbpTagHelperLocalizer.cs
@@ -10,7 +10,7 @@ public interface IAbpTagHelperLocalizer : ITransientDependency
 {
     string GetLocalizedText(string text, ModelExplorer explorer);
 
-    IStringLocalizer GetLocalizerOrNull(ModelExplorer explorer);
+    IStringLocalizer? GetLocalizerOrNull(ModelExplorer explorer);
 
-    IStringLocalizer GetLocalizerOrNull(Assembly assembly);
+    IStringLocalizer? GetLocalizerOrNull(Assembly assembly);
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/ListGroup/AbpListGroupItemTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/ListGroup/AbpListGroupItemTagHelper.cs
index 13ef2f4089..c116a2a980 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/ListGroup/AbpListGroupItemTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/ListGroup/AbpListGroupItemTagHelper.cs
@@ -6,7 +6,7 @@ public class AbpListGroupItemTagHelper : AbpTagHelper<AbpListGroupItemTagHelper,
 
     public bool? Disabled { get; set; }
 
-    public string Href { get; set; }
+    public string? Href { get; set; }
 
     public AbpListItemTagType TagType { get; set; } = AbpListItemTagType.Default;
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Modal/AbpModalHeaderTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Modal/AbpModalHeaderTagHelper.cs
index 44881ddb8c..832edd5774 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Modal/AbpModalHeaderTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Modal/AbpModalHeaderTagHelper.cs
@@ -2,7 +2,7 @@
 
 public class AbpModalHeaderTagHelper : AbpTagHelper<AbpModalHeaderTagHelper, AbpModalHeaderTagHelperService>
 {
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
     public AbpModalHeaderTagHelper(AbpModalHeaderTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/AbpNavbarToggleTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/AbpNavbarToggleTagHelper.cs
index 580bb29253..d0b4c5757f 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/AbpNavbarToggleTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/AbpNavbarToggleTagHelper.cs
@@ -2,7 +2,7 @@
 
 public class AbpNavbarToggleTagHelper : AbpTagHelper<AbpNavbarToggleTagHelper, AbpNavbarToggleTagHelperService>
 {
-    public string Id { get; set; }
+    public string? Id { get; set; }
 
     public AbpNavbarToggleTagHelper(AbpNavbarToggleTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/NavItem.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/NavItem.cs
index 00f494299b..e975207f09 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/NavItem.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Nav/NavItem.cs
@@ -2,7 +2,7 @@
 
 public class NavItem
 {
-    public string Html { get; set; }
+    public string Html { get; set; } = default!;
 
     public bool Active { get; set; }
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/AbpPaginationTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/AbpPaginationTagHelper.cs
index 35ec4ec65c..4c144bb92d 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/AbpPaginationTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/AbpPaginationTagHelper.cs
@@ -7,7 +7,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Pagination;
 [HtmlTargetElement("abp-paginator")]
 public class AbpPaginationTagHelper : AbpTagHelper<AbpPaginationTagHelper, AbpPaginationTagHelperService>
 {
-    public PagerModel Model { get; set; }
+    public PagerModel Model { get; set; } = default!;
 
     public bool? ShowInfo { get; set; }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PageItem.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PageItem.cs
index cf11fd6f0c..4f57d2b198 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PageItem.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PageItem.cs
@@ -16,7 +16,7 @@ public class PageItem
         IsGap = isGap;
     }
 
-    public override bool Equals(object obj)
+    public override bool Equals(object? obj)
     {
         if (!(obj is PageItem item))
         {
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PagerModel.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PagerModel.cs
index 814863f0e8..b592af59a3 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PagerModel.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Pagination/PagerModel.cs
@@ -25,13 +25,13 @@ public class PagerModel
 
     public int NextPage { get; set; }
 
-    public string Sort { get; set; }
+    public string? Sort { get; set; }
 
     public string PageUrl { get; set; }
 
     private const int MaxItemsCountToShowAllPages = 4;
 
-    public PagerModel(long totalCount, int shownItemsCount, int currentPage, int pageSize, string pageUrl, string sort = null)
+    public PagerModel(long totalCount, int shownItemsCount, int currentPage, int pageSize, string pageUrl, string? sort = null)
     {
         TotalItemsCount = totalCount;
         ShownItemsCount = shownItemsCount;
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelper.cs
index 695b2acafe..69331db6d3 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelper.cs
@@ -20,15 +20,15 @@ public class AbpPopoverTagHelper : AbpTagHelper<AbpPopoverTagHelper, AbpPopoverT
 
     public bool? Hoverable { get; set; }
 
-    public string AbpPopover { get; set; }
+    public string? AbpPopover { get; set; }
 
-    public string AbpPopoverRight { get; set; }
+    public string? AbpPopoverRight { get; set; }
 
-    public string AbpPopoverLeft { get; set; }
+    public string? AbpPopoverLeft { get; set; }
 
-    public string AbpPopoverTop { get; set; }
+    public string? AbpPopoverTop { get; set; }
 
-    public string AbpPopoverBottom { get; set; }
+    public string? AbpPopoverBottom { get; set; }
 
     public AbpPopoverTagHelper(AbpPopoverTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelperService.cs
index c4ee267f9f..2a1989f996 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Popover/AbpPopoverTagHelperService.cs
@@ -124,15 +124,15 @@ public class AbpPopoverTagHelperService : AbpTagHelperService<AbpPopoverTagHelpe
         switch (GetDirectory())
         {
             case PopoverDirectory.Top:
-                return TagHelper.AbpPopoverTop;
+                return TagHelper.AbpPopoverTop!;
             case PopoverDirectory.Right:
-                return TagHelper.AbpPopoverRight;
+                return TagHelper.AbpPopoverRight!;
             case PopoverDirectory.Bottom:
-                return TagHelper.AbpPopoverBottom;
+                return TagHelper.AbpPopoverBottom!;
             case PopoverDirectory.Left:
-                return TagHelper.AbpPopoverLeft;
+                return TagHelper.AbpPopoverLeft!;
             default:
-                return TagHelper.AbpPopover;
+                return TagHelper.AbpPopover!;
         }
     }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabDropdownTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabDropdownTagHelper.cs
index 5bc1d221c8..72b416e958 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabDropdownTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabDropdownTagHelper.cs
@@ -5,9 +5,9 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Tab;
 [HtmlTargetElement("abp-tab-dropdown")]
 public class AbpTabDropdownTagHelper : AbpTagHelper<AbpTabDropdownTagHelper, AbpTabDropdownTagHelperService>
 {
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
     public AbpTabDropdownTagHelper(AbpTabDropdownTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelper.cs
index fa0d89eec0..281db5ca06 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelper.cs
@@ -5,13 +5,13 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Tab;
 [HtmlTargetElement("abp-tab-link", TagStructure = TagStructure.WithoutEndTag)]
 public class AbpTabLinkTagHelper : AbpTagHelper<AbpTabLinkTagHelper, AbpTabLinkTagHelperService>
 {
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
-    public string ParentDropdownName { get; set; }
+    public string? ParentDropdownName { get; set; }
 
-    public string Href { get; set; }
+    public string Href { get; set; } = default!;
 
     public AbpTabLinkTagHelper(AbpTabLinkTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelperService.cs
index 5e0766c1af..2a7555021c 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabLinkTagHelperService.cs
@@ -16,7 +16,7 @@ public class AbpTabLinkTagHelperService : AbpTagHelperService<AbpTabLinkTagHelpe
 
         var tabHeaderItems = context.GetValue<List<TabItem>>(TabItems);
 
-        tabHeaderItems.Add(new TabItem(tabHeader, "", false, TagHelper.Name, TagHelper.ParentDropdownName, false));
+        tabHeaderItems.Add(new TabItem(tabHeader, "", false, TagHelper.Name!, TagHelper.ParentDropdownName, false));
 
         output.SuppressOutput();
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelper.cs
index 17f583e020..67bbbb3675 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelper.cs
@@ -5,13 +5,13 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Tab;
 [HtmlTargetElement("abp-tab")]
 public class AbpTabTagHelper : AbpTagHelper<AbpTabTagHelper, AbpTabTagHelperService>
 {
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
-    public string Title { get; set; }
+    public string Title { get; set; } = default!;
 
     public bool? Active { get; set; }
 
-    public string ParentDropdownName { get; set; }
+    public string? ParentDropdownName { get; set; }
 
     public AbpTabTagHelper(AbpTabTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelperService.cs
index cac1cf231d..227bc0fd71 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabTagHelperService.cs
@@ -21,7 +21,7 @@ public class AbpTabTagHelperService : AbpTagHelperService<AbpTabTagHelper>
 
         var active = TagHelper.Active ?? false;
 
-        tabHeaderItems.Add(new TabItem(tabHeader, tabContent, active, TagHelper.Name, TagHelper.ParentDropdownName, false));
+        tabHeaderItems.Add(new TabItem(tabHeader, tabContent, active, TagHelper.Name!, TagHelper.ParentDropdownName, false));
 
         output.SuppressOutput();
     }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabsTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabsTagHelper.cs
index dced93a11c..141ca82d83 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabsTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/AbpTabsTagHelper.cs
@@ -5,7 +5,7 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Tab;
 
 public class AbpTabsTagHelper : AbpTagHelper<AbpTabsTagHelper, AbpTabsTagHelperService>
 {
-    public string Name { get; set; }
+    public string? Name { get; set; }
 
     public TabStyle TabStyle { get; set; } = TabStyle.Tab;
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/TabItem.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/TabItem.cs
index 5f10a4b89d..f1e7b13767 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/TabItem.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tab/TabItem.cs
@@ -2,7 +2,7 @@
 
 public class TabItem
 {
-    public TabItem(string header, string content, bool active, string id, string parentId, bool isDropdown)
+    public TabItem(string header, string content, bool active, string id, string? parentId, bool isDropdown)
     {
         Header = header;
         Content = content;
@@ -22,5 +22,5 @@ public class TabItem
 
     public string Id { get; set; }
 
-    public string ParentId { get; set; }
+    public string? ParentId { get; set; }
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelper.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelper.cs
index b1fda858d3..6cdc0ba9f9 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelper.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelper.cs
@@ -14,17 +14,17 @@ namespace Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.TagHelpers.Tooltip;
 [HtmlTargetElement("abp-button", Attributes = "abp-tooltip-bottom")]
 public class AbpTooltipTagHelper : AbpTagHelper<AbpTooltipTagHelper, AbpTooltipTagHelperService>
 {
-    public string AbpTooltip { get; set; }
+    public string? AbpTooltip { get; set; }
 
-    public string AbpTooltipRight { get; set; }
+    public string? AbpTooltipRight { get; set; }
 
-    public string AbpTooltipLeft { get; set; }
+    public string? AbpTooltipLeft { get; set; }
 
-    public string AbpTooltipTop { get; set; }
+    public string? AbpTooltipTop { get; set; }
 
-    public string AbpTooltipBottom { get; set; }
+    public string? AbpTooltipBottom { get; set; }
 
-    public string Title { get; set; }
+    public string? Title { get; set; }
 
     public AbpTooltipTagHelper(AbpTooltipTagHelperService tagHelperService)
         : base(tagHelperService)
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelperService.cs b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelperService.cs
index 429a58b54b..dc5ce59328 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelperService.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/TagHelpers/Tooltip/AbpTooltipTagHelperService.cs
@@ -59,15 +59,15 @@ public class AbpTooltipTagHelperService : AbpTagHelperService<AbpTooltipTagHelpe
         switch (GetDirectory())
         {
             case TooltipDirectory.Top:
-                return TagHelper.AbpTooltipTop;
+                return TagHelper.AbpTooltipTop!;
             case TooltipDirectory.Right:
-                return TagHelper.AbpTooltipRight;
+                return TagHelper.AbpTooltipRight!;
             case TooltipDirectory.Bottom:
-                return TagHelper.AbpTooltipBottom;
+                return TagHelper.AbpTooltipBottom!;
             case TooltipDirectory.Left:
-                return TagHelper.AbpTooltipLeft;
+                return TagHelper.AbpTooltipLeft!;
             default:
-                return TagHelper.AbpTooltip;
+                return TagHelper.AbpTooltip!;
         }
     }
 
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.csproj b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.csproj
index 75b09d631b..1480dc0de1 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.csproj
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap/Volo.Abp.AspNetCore.Mvc.UI.Bootstrap.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AddRazorSupportForMvc>true</AddRazorSupportForMvc>
     <AssemblyName>Volo.Abp.AspNetCore.Mvc.UI.Bootstrap</AssemblyName>
     <PackageId>Volo.Abp.AspNetCore.Mvc.UI.Bootstrap</PackageId>
diff --git a/framework/src/Volo.Abp.BackgroundJobs.HangFire/Volo/Abp/BackgroundJobs/Hangfire/AbpDashboardOptionsProvider.cs b/framework/src/Volo.Abp.BackgroundJobs.HangFire/Volo/Abp/BackgroundJobs/Hangfire/AbpDashboardOptionsProvider.cs
index bc41b21ce8..b5277abe34 100644
--- a/framework/src/Volo.Abp.BackgroundJobs.HangFire/Volo/Abp/BackgroundJobs/Hangfire/AbpDashboardOptionsProvider.cs
+++ b/framework/src/Volo.Abp.BackgroundJobs.HangFire/Volo/Abp/BackgroundJobs/Hangfire/AbpDashboardOptionsProvider.cs
@@ -3,7 +3,7 @@ using Hangfire;
 using Microsoft.Extensions.Options;
 using Volo.Abp.DependencyInjection;
 
-namespace Volo.Abp.BackgroundJobs.Hangfire;
+`namespace Volo.Abp.BackgroundJobs.Hangfire;
 
 public class AbpDashboardOptionsProvider : ITransientDependency
 {