diff --git a/framework/src/Volo.Abp.AspNetCore.Components.Web.Theming.MudBlazor/Components/PageHeader.razor.cs b/framework/src/Volo.Abp.AspNetCore.Components.Web.Theming.MudBlazor/Components/PageHeader.razor.cs
index b092fa1a2e..379adc958c 100644
--- a/framework/src/Volo.Abp.AspNetCore.Components.Web.Theming.MudBlazor/Components/PageHeader.razor.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Components.Web.Theming.MudBlazor/Components/PageHeader.razor.cs
@@ -4,7 +4,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
-using Volo.Abp.AspNetCore.Components.Web.Theming;
+using Volo.Abp.AspNetCore.Components.Web.Theming.Layout;
 using Volo.Abp.AspNetCore.Components.Web.Theming.PageToolbars;
 using Volo.Abp.BlazoriseUI;
 
diff --git a/framework/src/Volo.Abp.MudBlazorUI/Components/AbpMudExtensibleDataGrid.razor.cs b/framework/src/Volo.Abp.MudBlazorUI/Components/AbpMudExtensibleDataGrid.razor.cs
index bfc0b06f62..15afdfc47c 100644
--- a/framework/src/Volo.Abp.MudBlazorUI/Components/AbpMudExtensibleDataGrid.razor.cs
+++ b/framework/src/Volo.Abp.MudBlazorUI/Components/AbpMudExtensibleDataGrid.razor.cs
@@ -6,6 +6,7 @@ using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Localization.Resources.AbpUi;
 using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.Extensions.Localization;
 using MudBlazor;
 using Volo.Abp.AspNetCore.Components.Web.Extensibility.TableColumns;
@@ -47,8 +48,8 @@ public partial class AbpMudExtensibleDataGrid<TItem> : ComponentBase
     {
         return (builder) =>
         {
-            builder.OpenComponent(type);
-            builder.AddAttribute(0, DataFieldAttributeName, data);
+            builder.OpenComponent(0, type);
+            builder.AddAttribute(1, DataFieldAttributeName, data);
             builder.CloseComponent();
         };
     }
diff --git a/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor b/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor
index 9e4e010504..812049a795 100644
--- a/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor
+++ b/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor
@@ -1,3 +1,4 @@
+#nullable enable
 @typeparam TEntity
 @typeparam TResourceType
 @using Volo.Abp.Localization
@@ -5,7 +6,7 @@
 
 @if (PropertyInfo != null && Entity != null)
 {
-    <MudAutocomplete T="MudSelectItem<object>?"
+    <MudAutocomplete T="MudSelectItem<object>"
                      Label="@PropertyInfo.GetLocalizedDisplayName(StringLocalizerFactory)"
                      Value="@SelectedItem"
                      ValueChanged="@SelectedItemChanged"
diff --git a/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor.cs b/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor.cs
index f9a6a6e66a..a9b75b99b5 100644
--- a/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor.cs
+++ b/framework/src/Volo.Abp.MudBlazorUI/Components/ObjectExtending/MudLookupExtensionProperty.razor.cs
@@ -19,7 +19,12 @@ public partial class MudLookupExtensionProperty<TEntity, TResourceType>
 
     public string TextPropertyName => PropertyInfo.Name + "_Text";
 
-    public MudSelectItem<object>? SelectedItem { get; set; }
+    private MudSelectItem<object>? _selectedItem;
+
+    public MudSelectItem<object> SelectedItem {
+        get => _selectedItem!;
+        set => _selectedItem = value;
+    }
 
     public object? SelectedValue
     {
@@ -68,7 +73,7 @@ public partial class MudLookupExtensionProperty<TEntity, TResourceType>
         var selectItems = new List<MudSelectItem<object>>();
 
         var url = PropertyInfo.Lookup.Url;
-        if (!filter.IsNullOrEmpty())
+        if (!string.IsNullOrEmpty(filter))
         {
             url += $"?{PropertyInfo.Lookup.FilterParamName}={filter.Trim()}";
         }
@@ -89,7 +94,7 @@ public partial class MudLookupExtensionProperty<TEntity, TResourceType>
         return selectItems;
     }
 
-    protected virtual Task SelectedItemChanged(MudSelectItem<object>? item)
+    protected virtual Task SelectedItemChanged(MudSelectItem<object> item)
     {
         SelectedItem = item;
         SelectedValue = item?.Value;