diff --git a/src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj b/src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj
index 2ee211b2..0b60675f 100644
--- a/src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj
+++ b/src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj
@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <Description>Versatile OpenID Connect stack for ASP.NET Core 2.1, 3.1 and 5.0.</Description>
+    <Description>Versatile OpenID Connect stack for ASP.NET Core.</Description>
     <PackageTags>$(PackageTags);aspnetcore;server;validation</PackageTags>
   </PropertyGroup>
 
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
index d20076d0..9a9ae12a 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
@@ -1002,7 +1002,7 @@ public class OpenIddictEntityFrameworkApplicationStore<TApplication, TAuthorizat
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
index 429b068c..c04612ff 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
@@ -877,7 +877,7 @@ public class OpenIddictEntityFrameworkAuthorizationStore<TAuthorization, TApplic
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
index 0b0400a6..4dba6b40 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
@@ -702,7 +702,7 @@ public class OpenIddictEntityFrameworkScopeStore<TScope, TContext, TKey> : IOpen
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
index 7f099579..0d55be05 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
@@ -908,7 +908,7 @@ public class OpenIddictEntityFrameworkTokenStore<TToken, TApplication, TAuthoriz
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
index 72fef57d..1c961318 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
@@ -1043,7 +1043,7 @@ public class OpenIddictEntityFrameworkCoreApplicationStore<TApplication, TAuthor
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
index 2b7c158c..6b829832 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
@@ -476,7 +476,7 @@ public class OpenIddictEntityFrameworkCoreAuthorizationStore<TAuthorization, TAp
             throw new ArgumentNullException(nameof(authorization));
         }
 
-        if (authorization.CreationDate == null)
+        if (authorization.CreationDate is null)
         {
             return new ValueTask<DateTimeOffset?>(result: null);
         }
@@ -966,7 +966,7 @@ public class OpenIddictEntityFrameworkCoreAuthorizationStore<TAuthorization, TAp
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
index 04fefdea..7a85aa8a 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
@@ -718,7 +718,7 @@ public class OpenIddictEntityFrameworkCoreScopeStore<TScope, TContext, TKey> : I
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
index 7279a075..77c36401 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
@@ -984,7 +984,7 @@ public class OpenIddictEntityFrameworkCoreTokenStore<TToken, TApplication, TAuth
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>