使用 C# 中的委托创建异步等待 function

Question

I have the following delegates that I need to make them async await .

My delegate:

public delegate bool GetUserFromAccessTokenHandler(string token, out User user);

public GetUserFromAccessTokenHandler GetUserFromAccessToken;

public FunctionalOperations(IUnitOfWork unitOfWork)
{
      GetUserFromAccessToken = new GetUserFromAccessTokenHandler(GetUserFromAccessTokenFunction);
      _unitOfWork = unitOfWork;
}

Now I need to add async to the method GetUserFromAccessTokenFunction but an error occurs:

private async bool GetUserFromAccessTokenFunction (string token, out User user)
{
     var x = await _unitOfWork.User.Get(...);
}

The two errors that I get are:

1. The call is ambiguous between the following methods or properties: 'GetUserFromAccessTokenFunction' and 'GetUserFromAccessTokenFunction'

2. The return type of an async method must be void, Task or Task<T>

How can I fix my delegate declaration to fit my needs?

Answer 1

1. In async Methods you can not use out or ref parameter, read why you can't
2. asyn Method, return specific Async return types such Task , Task<T> , void , IAsyncEnumerable<T>

your code should look like the following

using System.Threading.Tasks; // Task Namespace

//...

public delegate Task<User> GetUserFromAccessTokenHandler(string token);

public GetUserFromAccessTokenHandler GetUserFromAccessToken;

public FunctionalOperations(IUnitOfWork unitOfWork)
{
      GetUserFromAccessToken = new GetUserFromAccessTokenHandler(GetUserFromAccessTokenFunction);
      _unitOfWork = unitOfWork;
}

private async Task<User> GetUserFromAccessTokenFunction (string token)
{
     var x = await _unitOfWork.User.Get(...);
     // ...
     return new User(); 
}