diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo.Abp.Authorization.Abstractions.csproj b/framework/src/Volo.Abp.Authorization.Abstractions/Volo.Abp.Authorization.Abstractions.csproj
index 86f6a8498a..51e05677d4 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo.Abp.Authorization.Abstractions.csproj
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo.Abp.Authorization.Abstractions.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.Authorization.Abstractions</AssemblyName>
         <PackageId>Volo.Abp.Authorization.Abstractions</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/AlwaysAllowAuthorizationService.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/AlwaysAllowAuthorizationService.cs
index 92de7873f8..b65bc7aa84 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/AlwaysAllowAuthorizationService.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/AlwaysAllowAuthorizationService.cs
@@ -21,12 +21,12 @@ public class AlwaysAllowAuthorizationService : IAbpAuthorizationService
         _currentPrincipalAccessor = currentPrincipalAccessor;
     }
 
-    public Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, IEnumerable<IAuthorizationRequirement> requirements)
+    public Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object? resource, IEnumerable<IAuthorizationRequirement> requirements)
     {
         return Task.FromResult(AuthorizationResult.Success());
     }
 
-    public Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object resource, string policyName)
+    public Task<AuthorizationResult> AuthorizeAsync(ClaimsPrincipal user, object? resource, string policyName)
     {
         return Task.FromResult(AuthorizationResult.Success());
     }
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/AlwaysAllowPermissionChecker.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/AlwaysAllowPermissionChecker.cs
index 703ed1c94a..7910750fe7 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/AlwaysAllowPermissionChecker.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/AlwaysAllowPermissionChecker.cs
@@ -17,7 +17,7 @@ public class AlwaysAllowPermissionChecker : IPermissionChecker
         return TaskCache.TrueResult;
     }
 
-    public Task<bool> IsGrantedAsync(ClaimsPrincipal claimsPrincipal, string name)
+    public Task<bool> IsGrantedAsync(ClaimsPrincipal? claimsPrincipal, string name)
     {
         return TaskCache.TrueResult;
     }
@@ -27,7 +27,7 @@ public class AlwaysAllowPermissionChecker : IPermissionChecker
         return IsGrantedAsync(null, names);
     }
 
-    public Task<MultiplePermissionGrantResult> IsGrantedAsync(ClaimsPrincipal claimsPrincipal, string[] names)
+    public Task<MultiplePermissionGrantResult> IsGrantedAsync(ClaimsPrincipal? claimsPrincipal, string[] names)
     {
         return Task.FromResult(new MultiplePermissionGrantResult(names, PermissionGrantResult.Granted));
     }
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/ICanAddChildPermission.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/ICanAddChildPermission.cs
index 57a224699f..828e4cbd01 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/ICanAddChildPermission.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/ICanAddChildPermission.cs
@@ -8,7 +8,7 @@ public interface ICanAddChildPermission
 {
     PermissionDefinition AddPermission(
         [NotNull] string name,
-        ILocalizableString displayName = null,
+        ILocalizableString? displayName = null,
         MultiTenancySides multiTenancySide = MultiTenancySides.Both,
         bool isEnabled = true);
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionChecker.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionChecker.cs
index 4dfc3b94c6..15bdeabcca 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionChecker.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionChecker.cs
@@ -8,9 +8,9 @@ public interface IPermissionChecker
 {
     Task<bool> IsGrantedAsync([NotNull] string name);
 
-    Task<bool> IsGrantedAsync([CanBeNull] ClaimsPrincipal claimsPrincipal, [NotNull] string name);
+    Task<bool> IsGrantedAsync(ClaimsPrincipal? claimsPrincipal, [NotNull] string name);
 
     Task<MultiplePermissionGrantResult> IsGrantedAsync([NotNull] string[] names);
 
-    Task<MultiplePermissionGrantResult> IsGrantedAsync([CanBeNull] ClaimsPrincipal claimsPrincipal, [NotNull] string[] names);
+    Task<MultiplePermissionGrantResult> IsGrantedAsync(ClaimsPrincipal? claimsPrincipal, [NotNull] string[] names);
 }
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionDefinitionContext.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionDefinitionContext.cs
index 411b030b6a..4f686a6bae 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionDefinitionContext.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/IPermissionDefinitionContext.cs
@@ -25,8 +25,7 @@ public interface IPermissionDefinitionContext
     /// </summary>
     /// <param name="name">Name of the group</param>
     /// <returns></returns>
-    [CanBeNull]
-    PermissionGroupDefinition GetGroupOrNull(string name);
+    PermissionGroupDefinition? GetGroupOrNull(string name);
 
     /// <summary>
     /// Tries to add a new permission group.
@@ -37,7 +36,7 @@ public interface IPermissionDefinitionContext
     /// </summary>
     PermissionGroupDefinition AddGroup(
         [NotNull] string name,
-        ILocalizableString displayName = null);
+        ILocalizableString? displayName = null);
 
     /// <summary>
     /// Tries to remove a permission group.
@@ -51,6 +50,5 @@ public interface IPermissionDefinitionContext
     /// Returns null if can not find the given group.
     /// <param name="name">Name of the group</param>
     /// </summary>
-    [CanBeNull]
-    PermissionDefinition GetPermissionOrNull([NotNull] string name);
+    PermissionDefinition? GetPermissionOrNull([NotNull] string name);
 }
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinition.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinition.cs
index fb6f07690c..ab49e4aad4 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinition.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinition.cs
@@ -20,7 +20,7 @@ public class PermissionDefinition :
     /// Parent of this permission if one exists.
     /// If set, this permission can be granted only if parent is granted.
     /// </summary>
-    public PermissionDefinition Parent { get; private set; }
+    public PermissionDefinition? Parent { get; private set; }
 
     /// <summary>
     /// MultiTenancy side.
@@ -40,7 +40,7 @@ public class PermissionDefinition :
         get => _displayName;
         set => _displayName = Check.NotNull(value, nameof(value));
     }
-    private ILocalizableString _displayName;
+    private ILocalizableString _displayName = default!;
 
     public IReadOnlyList<PermissionDefinition> Children => _children.ToImmutableList();
     private readonly List<PermissionDefinition> _children;
@@ -48,7 +48,7 @@ public class PermissionDefinition :
     /// <summary>
     /// Can be used to get/set custom properties for this permission definition.
     /// </summary>
-    public Dictionary<string, object> Properties { get; }
+    public Dictionary<string, object?> Properties { get; }
 
     /// <summary>
     /// Indicates whether this permission is enabled or disabled.
@@ -71,14 +71,14 @@ public class PermissionDefinition :
     /// Returns the value in the <see cref="Properties"/> dictionary by given <paramref name="name"/>.
     /// Returns null if given <paramref name="name"/> is not present in the <see cref="Properties"/> dictionary.
     /// </returns>
-    public object this[string name] {
+    public object? this[string name] {
         get => Properties.GetOrDefault(name);
         set => Properties[name] = value;
     }
 
     protected internal PermissionDefinition(
         [NotNull] string name,
-        ILocalizableString displayName = null,
+        ILocalizableString? displayName = null,
         MultiTenancySides multiTenancySide = MultiTenancySides.Both,
         bool isEnabled = true)
     {
@@ -87,7 +87,7 @@ public class PermissionDefinition :
         MultiTenancySide = multiTenancySide;
         IsEnabled = isEnabled;
 
-        Properties = new Dictionary<string, object>();
+        Properties = new Dictionary<string, object?>();
         Providers = new List<string>();
         StateCheckers = new List<ISimpleStateChecker<PermissionDefinition>>();
         _children = new List<PermissionDefinition>();
@@ -95,7 +95,7 @@ public class PermissionDefinition :
 
     public virtual PermissionDefinition AddChild(
         [NotNull] string name,
-        ILocalizableString displayName = null,
+        ILocalizableString? displayName = null,
         MultiTenancySides multiTenancySide = MultiTenancySides.Both,
         bool isEnabled = true)
     {
@@ -115,7 +115,7 @@ public class PermissionDefinition :
     
     PermissionDefinition ICanAddChildPermission.AddPermission(
         string name,
-        ILocalizableString displayName = null,
+        ILocalizableString? displayName = null,
         MultiTenancySides multiTenancySide = MultiTenancySides.Both,
         bool isEnabled = true)
     {
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinitionContext.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinitionContext.cs
index 5b5543e868..4372046e15 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinitionContext.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionDefinitionContext.cs
@@ -20,7 +20,7 @@ public class PermissionDefinitionContext : IPermissionDefinitionContext
 
     public virtual PermissionGroupDefinition AddGroup(
         string name,
-        ILocalizableString displayName = null)
+        ILocalizableString? displayName = null)
     {
         Check.NotNull(name, nameof(name));
 
@@ -45,7 +45,7 @@ public class PermissionDefinitionContext : IPermissionDefinitionContext
         return group;
     }
 
-    public virtual PermissionGroupDefinition GetGroupOrNull([NotNull] string name)
+    public virtual PermissionGroupDefinition? GetGroupOrNull([NotNull] string name)
     {
         Check.NotNull(name, nameof(name));
 
@@ -69,7 +69,7 @@ public class PermissionDefinitionContext : IPermissionDefinitionContext
         Groups.Remove(name);
     }
 
-    public virtual PermissionDefinition GetPermissionOrNull([NotNull] string name)
+    public virtual PermissionDefinition? GetPermissionOrNull([NotNull] string name)
     {
         Check.NotNull(name, nameof(name));
 
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGrantInfo.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGrantInfo.cs
index 80031e5ea2..d348aeef79 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGrantInfo.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGrantInfo.cs
@@ -8,11 +8,11 @@ public class PermissionGrantInfo
 
     public bool IsGranted { get; }
 
-    public string ProviderName { get; }
+    public string? ProviderName { get; }
 
-    public string ProviderKey { get; }
+    public string? ProviderKey { get; }
 
-    public PermissionGrantInfo([NotNull] string name, bool isGranted, [CanBeNull] string providerName = null, [CanBeNull] string providerKey = null)
+    public PermissionGrantInfo([NotNull] string name, bool isGranted, string? providerName = null, string? providerKey = null)
     {
         Check.NotNull(name, nameof(name));
 
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGroupDefinition.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGroupDefinition.cs
index 9fd904f54c..bbc6e96cdf 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGroupDefinition.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionGroupDefinition.cs
@@ -13,13 +13,13 @@ public class PermissionGroupDefinition : ICanAddChildPermission
     /// </summary>
     public string Name { get; }
 
-    public Dictionary<string, object> Properties { get; }
+    public Dictionary<string, object?> Properties { get; }
 
     public ILocalizableString DisplayName {
         get => _displayName;
         set => _displayName = Check.NotNull(value, nameof(value));
     }
-    private ILocalizableString _displayName;
+    private ILocalizableString _displayName = default!;
 
     public IReadOnlyList<PermissionDefinition> Permissions => _permissions.ToImmutableList();
     private readonly List<PermissionDefinition> _permissions;
@@ -32,25 +32,25 @@ public class PermissionGroupDefinition : ICanAddChildPermission
     /// Returns the value in the <see cref="Properties"/> dictionary by given <paramref name="name"/>.
     /// Returns null if given <paramref name="name"/> is not present in the <see cref="Properties"/> dictionary.
     /// </returns>
-    public object this[string name] {
+    public object? this[string name] {
         get => Properties.GetOrDefault(name);
         set => Properties[name] = value;
     }
 
     protected internal PermissionGroupDefinition(
         string name,
-        ILocalizableString displayName = null)
+        ILocalizableString? displayName = null)
     {
         Name = name;
         DisplayName = displayName ?? new FixedLocalizableString(Name);
 
-        Properties = new Dictionary<string, object>();
+        Properties = new Dictionary<string, object?>();
         _permissions = new List<PermissionDefinition>();
     }
 
     public virtual PermissionDefinition AddPermission(
         [NotNull] string name,
-        ILocalizableString displayName = null,
+        ILocalizableString? displayName = null,
         MultiTenancySides multiTenancySide = MultiTenancySides.Both,
         bool isEnabled = true)
     {
@@ -93,15 +93,14 @@ public class PermissionGroupDefinition : ICanAddChildPermission
         return $"[{nameof(PermissionGroupDefinition)} {Name}]";
     }
 
-    [CanBeNull]
-    public PermissionDefinition GetPermissionOrNull([NotNull] string name)
+    public PermissionDefinition? GetPermissionOrNull([NotNull] string name)
     {
         Check.NotNull(name, nameof(name));
 
         return GetPermissionOrNullRecursively(Permissions, name);
     }
 
-    private PermissionDefinition GetPermissionOrNullRecursively(
+    private PermissionDefinition? GetPermissionOrNullRecursively(
         IReadOnlyList<PermissionDefinition> permissions, string name)
     {
         foreach (var permission in permissions)
diff --git a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionStateContext.cs b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionStateContext.cs
index a18aef117e..3398dd420e 100644
--- a/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionStateContext.cs
+++ b/framework/src/Volo.Abp.Authorization.Abstractions/Volo/Abp/Authorization/Permissions/PermissionStateContext.cs
@@ -4,7 +4,7 @@ namespace Volo.Abp.Authorization.Permissions;
 
 public class PermissionStateContext
 {
-    public IServiceProvider ServiceProvider { get; set; }
+    public IServiceProvider ServiceProvider { get; set; } = default!;
 
-    public PermissionDefinition Permission { get; set; }
+    public PermissionDefinition Permission { get; set; } = default!;
 }