使用 C# 中的委托創建異步等待 function

Question

我有以下委托，我需要讓他們async await 。

我的代表：

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

public GetUserFromAccessTokenHandler GetUserFromAccessToken;

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

現在我需要將異步添加到方法 GetUserFromAccessTokenFunction 但發生錯誤：

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

我得到的兩個錯誤是：

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>

如何修復我的代表聲明以滿足我的需求？

Answer 1

1. 在async方法中，您不能使用out或ref參數， 請閱讀為什么不能使用
2. asyn方法，返回特定的異步返回類型，例如Task 、 Task<T> 、 void 、 IAsyncEnumerable<T>

您的代碼應如下所示

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(); 
}