diff --git a/Directory.Build.props b/Directory.Build.props
index 8d70e562..ace8a1cd 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -4,6 +4,7 @@
 
   <PropertyGroup>
     <LangVersion>preview</LangVersion>
+    <AnalysisLevel>preview</AnalysisLevel>
     <NoWarn>$(NoWarn);CS1591;NU5118;NU5128</NoWarn>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <DebugSymbols>true</DebugSymbols>
diff --git a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
index 144853d0..7cb91e69 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
@@ -9,6 +9,7 @@ using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel.DataAnnotations;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Linq;
 using System.Runtime.CompilerServices;
@@ -22,7 +23,6 @@ using Microsoft.Extensions.Options;
 using OpenIddict.Abstractions;
 using static OpenIddict.Abstractions.OpenIddictConstants;
 using SR = OpenIddict.Abstractions.OpenIddictResources;
-using SuppressMessageAttribute = System.Diagnostics.CodeAnalysis.SuppressMessageAttribute;
 
 #if !SUPPORTS_KEY_DERIVATION_WITH_SPECIFIED_HASH_ALGORITHM
 using Org.BouncyCastle.Crypto;
@@ -445,7 +445,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return GetAsync((applications, state) => state(applications), query, cancellationToken);
+            return GetAsync(static (applications, query) => query(applications), query, cancellationToken);
         }
 
         /// <summary>
@@ -862,7 +862,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return ListAsync((applications, state) => state(applications), query, cancellationToken);
+            return ListAsync(static (applications, query) => query(applications), query, cancellationToken);
         }
 
         /// <summary>
diff --git a/src/OpenIddict.Core/Managers/OpenIddictAuthorizationManager.cs b/src/OpenIddict.Core/Managers/OpenIddictAuthorizationManager.cs
index 55d37f86..4803ba27 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictAuthorizationManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictAuthorizationManager.cs
@@ -656,7 +656,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return GetAsync((authorizations, state) => state(authorizations), query, cancellationToken);
+            return GetAsync(static (authorizations, query) => query(authorizations), query, cancellationToken);
         }
 
         /// <summary>
@@ -893,7 +893,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return ListAsync((authorizations, state) => state(authorizations), query, cancellationToken);
+            return ListAsync(static (authorizations, query) => query(authorizations), query, cancellationToken);
         }
 
         /// <summary>
diff --git a/src/OpenIddict.Core/Managers/OpenIddictScopeManager.cs b/src/OpenIddict.Core/Managers/OpenIddictScopeManager.cs
index 2d66c5b6..144dad6f 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictScopeManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictScopeManager.cs
@@ -383,7 +383,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return GetAsync((scopes, state) => state(scopes), query, cancellationToken);
+            return GetAsync(static (scopes, query) => query(scopes), query, cancellationToken);
         }
 
         /// <summary>
@@ -704,7 +704,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return ListAsync((scopes, state) => state(scopes), query, cancellationToken);
+            return ListAsync(static (scopes, query) => query(scopes), query, cancellationToken);
         }
 
         /// <summary>
diff --git a/src/OpenIddict.Core/Managers/OpenIddictTokenManager.cs b/src/OpenIddict.Core/Managers/OpenIddictTokenManager.cs
index 5a3d6508..dadf5a42 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictTokenManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictTokenManager.cs
@@ -622,7 +622,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return GetAsync((tokens, state) => state(tokens), query, cancellationToken);
+            return GetAsync(static (tokens, query) => query(tokens), query, cancellationToken);
         }
 
         /// <summary>
@@ -892,7 +892,7 @@ namespace OpenIddict.Core
                 throw new ArgumentNullException(nameof(query));
             }
 
-            return ListAsync((tokens, state) => state(tokens), query, cancellationToken);
+            return ListAsync(static (tokens, query) => query(tokens), query, cancellationToken);
         }
 
         /// <summary>
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkApplication.cs b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkApplication.cs
index 2e998737..c084f271 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkApplication.cs
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkApplication.cs
@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFramework.Models
 {
@@ -74,8 +73,7 @@ namespace OpenIddict.EntityFramework.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current application.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the permissions associated with the
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkAuthorization.cs b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkAuthorization.cs
index 0a68bdfd..84954f1b 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkAuthorization.cs
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkAuthorization.cs
@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFramework.Models
 {
@@ -50,8 +49,7 @@ namespace OpenIddict.EntityFramework.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current authorization.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the additional properties serialized as a JSON object,
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkScope.cs b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkScope.cs
index 04ab550e..34226a16 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkScope.cs
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkScope.cs
@@ -6,7 +6,6 @@
 
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFramework.Models
 {
@@ -59,8 +58,7 @@ namespace OpenIddict.EntityFramework.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current scope.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the unique name associated with the current scope.
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkToken.cs b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkToken.cs
index 3316071c..ae21cab6 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkToken.cs
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddictEntityFrameworkToken.cs
@@ -6,7 +6,6 @@
 
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFramework.Models
 {
@@ -59,8 +58,7 @@ namespace OpenIddict.EntityFramework.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current token.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the payload of the current token, if applicable.
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
index c10d2d3a..7d848d7e 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs
@@ -11,7 +11,6 @@ using System.ComponentModel;
 using System.Data;
 using System.Data.Entity;
 using System.Data.Entity.Infrastructure;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -862,8 +861,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -878,7 +876,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
index dca2714e..4e1bcddd 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs
@@ -11,7 +11,6 @@ using System.ComponentModel;
 using System.Data;
 using System.Data.Entity;
 using System.Data.Entity.Infrastructure;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text.Encodings.Web;
@@ -820,8 +819,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -836,7 +834,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
index 86f05910..feee3183 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs
@@ -10,7 +10,6 @@ using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Data.Entity;
 using System.Data.Entity.Infrastructure;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -630,8 +629,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -646,7 +644,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
index f537aa88..bcf47cda 100644
--- a/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
+++ b/src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs
@@ -11,7 +11,6 @@ using System.ComponentModel;
 using System.Data;
 using System.Data.Entity;
 using System.Data.Entity.Infrastructure;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text.Encodings.Web;
 using System.Text.Json;
@@ -848,8 +847,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -864,7 +862,7 @@ namespace OpenIddict.EntityFramework
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreApplication.cs b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreApplication.cs
index 5407240e..dd3135fd 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreApplication.cs
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreApplication.cs
@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFrameworkCore.Models
 {
@@ -82,8 +81,7 @@ namespace OpenIddict.EntityFrameworkCore.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current application.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the permissions associated with the
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreAuthorization.cs b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreAuthorization.cs
index 311a148a..2007b92b 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreAuthorization.cs
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreAuthorization.cs
@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFrameworkCore.Models
 {
@@ -58,8 +57,7 @@ namespace OpenIddict.EntityFrameworkCore.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current authorization.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the additional properties serialized as a JSON object,
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreScope.cs b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreScope.cs
index 3c2525b6..8d063b3c 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreScope.cs
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreScope.cs
@@ -6,7 +6,6 @@
 
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFrameworkCore.Models
 {
@@ -59,8 +58,7 @@ namespace OpenIddict.EntityFrameworkCore.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current scope.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the unique name associated with the current scope.
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreToken.cs b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreToken.cs
index 7c211f3b..4495b909 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreToken.cs
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddictEntityFrameworkCoreToken.cs
@@ -6,7 +6,6 @@
 
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 
 namespace OpenIddict.EntityFrameworkCore.Models
 {
@@ -67,8 +66,7 @@ namespace OpenIddict.EntityFrameworkCore.Models
         /// <summary>
         /// Gets or sets the unique identifier associated with the current token.
         /// </summary>
-        [AllowNull, MaybeNull]
-        public virtual TKey Id { get; set; } = default!;
+        public virtual TKey? Id { get; set; }
 
         /// <summary>
         /// Gets or sets the payload of the current token, if applicable.
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
index 2526d983..f60186dc 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs
@@ -9,7 +9,6 @@ using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Data;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -912,8 +911,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -928,7 +926,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
index 25282d3e..6e319ac8 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs
@@ -9,7 +9,6 @@ using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Data;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text.Encodings.Web;
@@ -905,8 +904,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -921,7 +919,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
index 8079129b..a2fa0282 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs
@@ -8,7 +8,6 @@ using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -646,8 +645,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -662,7 +660,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
index 8d1dc3bf..4dd14382 100644
--- a/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
+++ b/src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs
@@ -9,7 +9,6 @@ using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Data;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text.Encodings.Web;
 using System.Text.Json;
@@ -918,8 +917,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>An instance of <typeparamref name="TKey"/> representing the provided identifier.</returns>
-        [return: MaybeNull]
-        public virtual TKey ConvertIdentifierFromString(string? identifier)
+        public virtual TKey? ConvertIdentifierFromString(string? identifier)
         {
             if (string.IsNullOrEmpty(identifier))
             {
@@ -934,7 +932,7 @@ namespace OpenIddict.EntityFrameworkCore
         /// </summary>
         /// <param name="identifier">The identifier to convert.</param>
         /// <returns>A <see cref="string"/> representation of the provided identifier.</returns>
-        public virtual string? ConvertIdentifierToString([AllowNull] TKey identifier)
+        public virtual string? ConvertIdentifierToString(TKey? identifier)
         {
             if (Equals(identifier, default(TKey)))
             {
diff --git a/src/OpenIddict.Server/OpenIddictServerBuilder.cs b/src/OpenIddict.Server/OpenIddictServerBuilder.cs
index 4360c644..fba838b4 100644
--- a/src/OpenIddict.Server/OpenIddictServerBuilder.cs
+++ b/src/OpenIddict.Server/OpenIddictServerBuilder.cs
@@ -6,6 +6,7 @@
 
 using System;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -17,7 +18,6 @@ using Microsoft.IdentityModel.Tokens;
 using OpenIddict.Server;
 using static OpenIddict.Abstractions.OpenIddictConstants;
 using SR = OpenIddict.Abstractions.OpenIddictResources;
-using SuppressMessageAttribute = System.Diagnostics.CodeAnalysis.SuppressMessageAttribute;
 
 namespace Microsoft.Extensions.DependencyInjection
 {
diff --git a/src/OpenIddict.Validation/OpenIddictValidationBuilder.cs b/src/OpenIddict.Validation/OpenIddictValidationBuilder.cs
index b8cfd52a..fe7aeab9 100644
--- a/src/OpenIddict.Validation/OpenIddictValidationBuilder.cs
+++ b/src/OpenIddict.Validation/OpenIddictValidationBuilder.cs
@@ -6,6 +6,7 @@
 
 using System;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -16,7 +17,6 @@ using Microsoft.IdentityModel.Protocols.OpenIdConnect;
 using Microsoft.IdentityModel.Tokens;
 using OpenIddict.Validation;
 using SR = OpenIddict.Abstractions.OpenIddictResources;
-using SuppressMessageAttribute = System.Diagnostics.CodeAnalysis.SuppressMessageAttribute;
 
 namespace Microsoft.Extensions.DependencyInjection
 {