Replace new() constraints by Activator.CreateInstance() to allow using abstract entities as generic parameters

src/OpenIddict.EntityFramework/OpenIddictEntityFrameworkBuilder.cs

@@ -94,10 +94,10 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictEntityFrameworkBuilder"/>.</returns>
         public OpenIddictEntityFrameworkBuilder ReplaceDefaultEntities<TApplication, TAuthorization, TScope, TToken, TKey>()
-            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-            where TScope : OpenIddictScope<TKey>, new()
-            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+            where TScope : OpenIddictScope<TKey>
+            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
             where TKey : IEquatable<TKey>
         {
             Services.Configure<OpenIddictCoreOptions>(options =>

src/OpenIddict.EntityFramework/OpenIddictEntityFrameworkExtensions.cs

@@ -98,10 +98,10 @@ namespace Microsoft.Extensions.DependencyInjection
         /// <param name="builder">The builder used to configure the Entity Framework context.</param>
         /// <returns>The Entity Framework context builder.</returns>
         public static DbModelBuilder UseOpenIddict<TApplication, TAuthorization, TScope, TToken, TKey>([NotNull] this DbModelBuilder builder)
-            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-            where TScope : OpenIddictScope<TKey>, new()
-            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+            where TScope : OpenIddictScope<TKey>
+            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
             where TKey : IEquatable<TKey>
         {
             if (builder == null)

src/OpenIddict.EntityFramework/Stores/OpenIddictApplicationStore.cs

@@ -52,9 +52,9 @@ namespace OpenIddict.EntityFramework
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictApplicationStore<TApplication, TAuthorization, TToken, TContext, TKey> : IOpenIddictApplicationStore<TApplication>
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -651,7 +651,22 @@ namespace OpenIddict.EntityFramework
         /// whose result returns the instantiated application, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TApplication> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TApplication>(new TApplication());
+        {
+            try
+            {
+                return new ValueTask<TApplication>(Activator.CreateInstance<TApplication>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TApplication>(Task.FromException<TApplication>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new application instance.")
+                        .Append("Make sure that the application entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom application store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFramework/Stores/OpenIddictAuthorizationStore.cs

@@ -52,9 +52,9 @@ namespace OpenIddict.EntityFramework
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictAuthorizationStore<TAuthorization, TApplication, TToken, TContext, TKey> : IOpenIddictAuthorizationStore<TAuthorization>
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -574,7 +574,22 @@ namespace OpenIddict.EntityFramework
         /// whose result returns the instantiated authorization, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TAuthorization> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TAuthorization>(new TAuthorization());
+        {
+            try
+            {
+                return new ValueTask<TAuthorization>(Activator.CreateInstance<TAuthorization>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TAuthorization>(Task.FromException<TAuthorization>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new authorization instance.")
+                        .Append("Make sure that the authorization entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom authorization store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFramework/Stores/OpenIddictScopeStore.cs

@@ -46,7 +46,7 @@ namespace OpenIddict.EntityFramework
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictScopeStore<TScope, TContext, TKey> : IOpenIddictScopeStore<TScope>
-        where TScope : OpenIddictScope<TKey>, new()
+        where TScope : OpenIddictScope<TKey>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -439,7 +439,22 @@ namespace OpenIddict.EntityFramework
         /// whose result returns the instantiated scope, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TScope> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TScope>(new TScope());
+        {
+            try
+            {
+                return new ValueTask<TScope>(Activator.CreateInstance<TScope>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TScope>(Task.FromException<TScope>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new scope instance.")
+                        .Append("Make sure that the scope entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom scope store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFramework/Stores/OpenIddictTokenStore.cs

@@ -52,9 +52,9 @@ namespace OpenIddict.EntityFramework
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictTokenStore<TToken, TApplication, TAuthorization, TContext, TKey> : IOpenIddictTokenStore<TToken>
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -582,7 +582,22 @@ namespace OpenIddict.EntityFramework
         /// whose result returns the instantiated token, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TToken> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TToken>(new TToken());
+        {
+            try
+            {
+                return new ValueTask<TToken>(Activator.CreateInstance<TToken>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TToken>(Task.FromException<TToken>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new token instance.")
+                        .Append("Make sure that the token entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom token store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFrameworkCore/OpenIddictEntityFrameworkCoreBuilder.cs

@@ -103,10 +103,10 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictEntityFrameworkCoreBuilder"/>.</returns>
         public OpenIddictEntityFrameworkCoreBuilder ReplaceDefaultEntities<TApplication, TAuthorization, TScope, TToken, TKey>()
-            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-            where TScope : OpenIddictScope<TKey>, new()
-            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+            where TScope : OpenIddictScope<TKey>
+            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
             where TKey : IEquatable<TKey>
         {
             Services.Configure<OpenIddictCoreOptions>(options =>

src/OpenIddict.EntityFrameworkCore/OpenIddictEntityFrameworkCoreCustomizer.cs

@@ -18,10 +18,10 @@ namespace OpenIddict.EntityFrameworkCore
     /// required by the OpenIddict stack in an Entity Framework context.
     /// </summary>
     public class OpenIddictEntityFrameworkCoreCustomizer<TApplication, TAuthorization, TScope, TToken, TKey> : RelationalModelCustomizer
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-        where TScope : OpenIddictScope<TKey>, new()
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+        where TScope : OpenIddictScope<TKey>
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
         where TKey : IEquatable<TKey>
     {
         public OpenIddictEntityFrameworkCoreCustomizer([NotNull] ModelCustomizerDependencies dependencies)

src/OpenIddict.EntityFrameworkCore/OpenIddictEntityFrameworkCoreExtensions.cs

@@ -107,10 +107,10 @@ namespace Microsoft.Extensions.DependencyInjection
         /// <param name="builder">The builder used to configure the Entity Framework context.</param>
         /// <returns>The Entity Framework context builder.</returns>
         public static DbContextOptionsBuilder UseOpenIddict<TApplication, TAuthorization, TScope, TToken, TKey>([NotNull] this DbContextOptionsBuilder builder)
-            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-            where TScope : OpenIddictScope<TKey>, new()
-            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+            where TScope : OpenIddictScope<TKey>
+            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
             where TKey : IEquatable<TKey>
         {
             if (builder == null)
@@ -153,10 +153,10 @@ namespace Microsoft.Extensions.DependencyInjection
         /// <param name="builder">The builder used to configure the Entity Framework context.</param>
         /// <returns>The Entity Framework context builder.</returns>
         public static ModelBuilder UseOpenIddict<TApplication, TAuthorization, TScope, TToken, TKey>([NotNull] this ModelBuilder builder)
-            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-            where TScope : OpenIddictScope<TKey>, new()
-            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+            where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+            where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+            where TScope : OpenIddictScope<TKey>
+            where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
             where TKey : IEquatable<TKey>
         {
             if (builder == null)

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictApplicationStore.cs

@@ -74,9 +74,9 @@ namespace OpenIddict.EntityFrameworkCore
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictApplicationStore<TApplication, TAuthorization, TToken, TContext, TKey> : IOpenIddictApplicationStore<TApplication>
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -718,7 +718,22 @@ namespace OpenIddict.EntityFrameworkCore
         /// whose result returns the instantiated application, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TApplication> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TApplication>(new TApplication());
+        {
+            try
+            {
+                return new ValueTask<TApplication>(Activator.CreateInstance<TApplication>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TApplication>(Task.FromException<TApplication>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new application instance.")
+                        .Append("Make sure that the application entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom application store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictAuthorizationStore.cs

@@ -74,9 +74,9 @@ namespace OpenIddict.EntityFrameworkCore
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictAuthorizationStore<TAuthorization, TApplication, TToken, TContext, TKey> : IOpenIddictAuthorizationStore<TAuthorization>
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -662,7 +662,22 @@ namespace OpenIddict.EntityFrameworkCore
         /// whose result returns the instantiated authorization, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TAuthorization> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TAuthorization>(new TAuthorization());
+        {
+            try
+            {
+                return new ValueTask<TAuthorization>(Activator.CreateInstance<TAuthorization>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TAuthorization>(Task.FromException<TAuthorization>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new authorization instance.")
+                        .Append("Make sure that the authorization entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom authorization store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictScopeStore.cs

@@ -64,7 +64,7 @@ namespace OpenIddict.EntityFrameworkCore
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictScopeStore<TScope, TContext, TKey> : IOpenIddictScopeStore<TScope>
-        where TScope : OpenIddictScope<TKey>, new()
+        where TScope : OpenIddictScope<TKey>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -480,7 +480,22 @@ namespace OpenIddict.EntityFrameworkCore
         /// whose result returns the instantiated scope, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TScope> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TScope>(new TScope());
+        {
+            try
+            {
+                return new ValueTask<TScope>(Activator.CreateInstance<TScope>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TScope>(Task.FromException<TScope>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new scope instance.")
+                        .Append("Make sure that the scope entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom scope store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictTokenStore.cs

@@ -74,9 +74,9 @@ namespace OpenIddict.EntityFrameworkCore
     /// <typeparam name="TContext">The type of the Entity Framework database context.</typeparam>
     /// <typeparam name="TKey">The type of the entity primary keys.</typeparam>
     public class OpenIddictTokenStore<TToken, TApplication, TAuthorization, TContext, TKey> : IOpenIddictTokenStore<TToken>
-        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>, new()
-        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>, new()
-        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>, new()
+        where TToken : OpenIddictToken<TKey, TApplication, TAuthorization>
+        where TApplication : OpenIddictApplication<TKey, TAuthorization, TToken>
+        where TAuthorization : OpenIddictAuthorization<TKey, TApplication, TToken>
         where TContext : DbContext
         where TKey : IEquatable<TKey>
     {
@@ -660,7 +660,22 @@ namespace OpenIddict.EntityFrameworkCore
         /// whose result returns the instantiated token, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TToken> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TToken>(new TToken());
+        {
+            try
+            {
+                return new ValueTask<TToken>(Activator.CreateInstance<TToken>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TToken>(Task.FromException<TToken>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new token instance.")
+                        .Append("Make sure that the token entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom token store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.MongoDb/OpenIddictMongoDbBuilder.cs

@@ -78,7 +78,7 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictMongoDbBuilder"/>.</returns>
         public OpenIddictMongoDbBuilder ReplaceDefaultApplicationEntity<TApplication>()
-            where TApplication : OpenIddictApplication, new()
+            where TApplication : OpenIddictApplication
         {
             Services.Configure<OpenIddictCoreOptions>(options => options.DefaultApplicationType = typeof(TApplication));
 
@@ -90,7 +90,7 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictMongoDbBuilder"/>.</returns>
         public OpenIddictMongoDbBuilder ReplaceDefaultAuthorizationEntity<TAuthorization>()
-            where TAuthorization : OpenIddictAuthorization, new()
+            where TAuthorization : OpenIddictAuthorization
         {
             Services.Configure<OpenIddictCoreOptions>(options => options.DefaultAuthorizationType = typeof(TAuthorization));
 
@@ -102,7 +102,7 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictMongoDbBuilder"/>.</returns>
         public OpenIddictMongoDbBuilder ReplaceDefaultScopeEntity<TScope>()
-            where TScope : OpenIddictScope, new()
+            where TScope : OpenIddictScope
         {
             Services.Configure<OpenIddictCoreOptions>(options => options.DefaultScopeType = typeof(TScope));
 
@@ -114,7 +114,7 @@ namespace Microsoft.Extensions.DependencyInjection
         /// </summary>
         /// <returns>The <see cref="OpenIddictMongoDbBuilder"/>.</returns>
         public OpenIddictMongoDbBuilder ReplaceDefaultTokenEntity<TToken>()
-            where TToken : OpenIddictToken, new()
+            where TToken : OpenIddictToken
         {
             Services.Configure<OpenIddictCoreOptions>(options => options.DefaultTokenType = typeof(TToken));
 

src/OpenIddict.MongoDb/Stores/OpenIddictApplicationStore.cs

@@ -28,7 +28,7 @@ namespace OpenIddict.MongoDb
     /// </summary>
     /// <typeparam name="TApplication">The type of the Application entity.</typeparam>
     public class OpenIddictApplicationStore<TApplication> : IOpenIddictApplicationStore<TApplication>
-        where TApplication : OpenIddictApplication, new()
+        where TApplication : OpenIddictApplication
     {
         public OpenIddictApplicationStore(
             [NotNull] IMemoryCache cache,
@@ -490,7 +490,22 @@ namespace OpenIddict.MongoDb
         /// whose result returns the instantiated application, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TApplication> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TApplication>(new TApplication());
+        {
+            try
+            {
+                return new ValueTask<TApplication>(Activator.CreateInstance<TApplication>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TApplication>(Task.FromException<TApplication>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new application instance.")
+                        .Append("Make sure that the application entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom application store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.MongoDb/Stores/OpenIddictAuthorizationStore.cs

@@ -28,7 +28,7 @@ namespace OpenIddict.MongoDb
     /// </summary>
     /// <typeparam name="TAuthorization">The type of the Authorization entity.</typeparam>
     public class OpenIddictAuthorizationStore<TAuthorization> : IOpenIddictAuthorizationStore<TAuthorization>
-        where TAuthorization : OpenIddictAuthorization, new()
+        where TAuthorization : OpenIddictAuthorization
     {
         public OpenIddictAuthorizationStore(
             [NotNull] IMemoryCache cache,
@@ -489,7 +489,22 @@ namespace OpenIddict.MongoDb
         /// whose result returns the instantiated authorization, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TAuthorization> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TAuthorization>(new TAuthorization());
+        {
+            try
+            {
+                return new ValueTask<TAuthorization>(Activator.CreateInstance<TAuthorization>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TAuthorization>(Task.FromException<TAuthorization>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new authorization instance.")
+                        .Append("Make sure that the authorization entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom authorization store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.MongoDb/Stores/OpenIddictScopeStore.cs

@@ -28,7 +28,7 @@ namespace OpenIddict.MongoDb
     /// </summary>
     /// <typeparam name="TScope">The type of the Scope entity.</typeparam>
     public class OpenIddictScopeStore<TScope> : IOpenIddictScopeStore<TScope>
-        where TScope : OpenIddictScope, new()
+        where TScope : OpenIddictScope
     {
         public OpenIddictScopeStore(
             [NotNull] IMemoryCache cache,
@@ -394,7 +394,22 @@ namespace OpenIddict.MongoDb
         /// whose result returns the instantiated scope, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TScope> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TScope>(new TScope());
+        {
+            try
+            {
+                return new ValueTask<TScope>(Activator.CreateInstance<TScope>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TScope>(Task.FromException<TScope>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new scope instance.")
+                        .Append("Make sure that the scope entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom scope store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.

src/OpenIddict.MongoDb/Stores/OpenIddictTokenStore.cs

@@ -28,7 +28,7 @@ namespace OpenIddict.MongoDb
     /// </summary>
     /// <typeparam name="TToken">The type of the Token entity.</typeparam>
     public class OpenIddictTokenStore<TToken> : IOpenIddictTokenStore<TToken>
-        where TToken : OpenIddictToken, new()
+        where TToken : OpenIddictToken
     {
         public OpenIddictTokenStore(
             [NotNull] IMemoryCache cache,
@@ -507,7 +507,22 @@ namespace OpenIddict.MongoDb
         /// whose result returns the instantiated token, that can be persisted in the database.
         /// </returns>
         public virtual ValueTask<TToken> InstantiateAsync(CancellationToken cancellationToken)
-            => new ValueTask<TToken>(new TToken());
+        {
+            try
+            {
+                return new ValueTask<TToken>(Activator.CreateInstance<TToken>());
+            }
+
+            catch (MemberAccessException exception)
+            {
+                return new ValueTask<TToken>(Task.FromException<TToken>(
+                    new InvalidOperationException(new StringBuilder()
+                        .AppendLine("An error occurred while trying to create a new token instance.")
+                        .Append("Make sure that the token entity is not abstract and has a public parameterless constructor ")
+                        .Append("or create a custom token store that overrides 'InstantiateAsync()' to use a custom factory.")
+                        .ToString(), exception)));
+            }
+        }
 
         /// <summary>
         /// Executes the specified query and returns all the corresponding elements.