ValueTask<T> not working in Auto Interface Implementation, please provide support (System.Threading.Tasks.Extensions nuget package)

[keerthirajap]

Describe the feature

Please provide support for ValueTask used along with Auto Interface Implementation. ValueTask installed through System.Threading.Tasks.Extensions nuget package

Is this feature related to a problem, describe

User Model

    public class User
    {
        public long UserId { get; set; }

        public string UserName { get; set; }

        public string FirstName { get; set; }

        public string LastName { get; set; }
    }

IUserRepository.cs

 public interface IUserRepository
    {
        [Sql(@"SELECT [UserId]
                  ,[UserName]
                  ,[FirstName]
                  ,[LastName]
              FROM[dbo].[User]")]
        Task<List<User>> TaskGetAllUsersAsync();             **// This works**

        [Sql(@"SELECT [UserId]
                  ,[UserName]
                  ,[FirstName]
                  ,[LastName]
              FROM[dbo].[User]")]
        ValueTask<List<User>> ValueTaskGetAllUsersAsync();   **// This not working, return null value**
    }

Program.cs

        private static async Task Main(string[] args)
        {
            DbConnection c = new SqlConnection("");
            IUserRepository i = c.As<IUserRepository>();

            List<User> users = new List<User>();
            
            **// This works**
            users = await i.TaskGetAllUsersAsync();

           **// This not working, return null value**
            users = await i.ValueTaskGetAllUsersAsync();

            Console.ReadKey();
        }

Additional context

[andymac4182]

I am curious. What is the benefit of ValueTask over Task? My understanding was ValueTask was for situations where the function has the chance it would be executed synchronously. Is there another way it can be useful for this situation?

[lawrencek76]

@andymac4182 I think you are correct in your understanding. There may be other opportunities to expose valuetask for example BeginDbTransactionAsync Now returns valuetask so exposing those from the underlying DbCommand does make sense wherever possible.

See dotnet/runtime#28596

As far as adding It to the auto interface implementation I don’t see why it can’t be done but its seems like only a very few dB providers maybe none at this point would benefit.

[jonwagner]

Interface methods all go through paths that are almost guaranteed to do I/O.

Open => Exec => Read => Close

The Insight methods all return Task, so there's no benefit from supporting ValueTask.

I toyed around with supporting ValueTask as a return type. It's possible to do it for simplicity, but it would result in an additional allocation on each return.