需要帮助的同步控制事件处理程序在C＃中

Question

我有如下的代码片段：

public void PopulateItemList() 
{ 
    foreach(var item in collection) 
    { 
     bool isSuccess = GetSubItem(item.Id); 
     if(!isSuccess) 
     { 
      ShowError(); 
      break; 
     } 
    } 
} 

public bool GetSubItem(string parentId) 
{ 
    bool isSuccess = false; 
    _service.Communication<ViewModel, Request, Response>((ViewModel vm, ref Request) => 
    { 
     request.ApiName = Const.FXXXName; 
     request.Id = parentId; 
    }, (viewModel, response, error) => 
    { 
     DoSomething(); 
     ... 
     isSuccess = response.IsOk; // I put a breakpoint here 
    } 
    return isSuccess; // I also put a breakpoint here 
} 

通信功能的原型如下：

public void Communication<VM, S, R>(WebSocketOut<VM, S) send, WebSocketIn<VM, R> recv) 

其中WebSocketIn和WebSocketOut两个代表。问题是当我调试程序时，“return isSuccess;”语句总是在从“response.IsOk”收到结果之前运行，因此该func的返回值始终为“false”。换句话说，执行的顺序是：

1. 回报isSuccess
2. isSuccess = response.IsOk（之后的messageReceived（WebSocket4Net）触发的事件）

我不知道如何使它以相反的顺序运行。任何意见，建议或帮助将不胜感激。

感谢

Answer 1

您可以使用async/await和TaskCompletionSource

async public void PopulateItemList() //!!async keyword 
{ 
    foreach(var item in collection) 
    { 
     bool isSuccess = await GetSubItem(item.Id); //!!await 
     if(!isSuccess) 
     { 
      ShowError(); 
      break; 
     } 
    } 
} 

public Task<bool> GetSubItem(string parentId) 
{ 
    var tcs = new TaskCompletionSource<bool>(); //!! 
    _service.Communication<ViewModel, Request, Response>((ViewModel vm, ref Request) => 
    { 
     request.ApiName = Const.FXXXName; 
     request.Id = parentId; 
    }, (viewModel, response, error) => 
    { 
     DoSomething(); 
     ... 
     tcs.SetResult(response.IsOk); //!! 
    } 
    return tcs.Task; 
} 

Answer 2

尝试使用的AutoResetEvent等待异步功能齐全。

public bool GetSubItem(string parentId) 
{ 
    System.Threading.AutoResetEvent autoEvent = new System.Threading.AutoResetEvent(false); 

    bool isSuccess = false; 

    ThreadPool.QueueUserWorkItem((o) => 
    { 
     _service.Communication<ViewModel, Request, Response>((ViewModel vm, ref Request) => 
     { 
      request.ApiName = Const.FXXXName; 
      request.Id = parentId; 
     }, (viewModel, response, error) => 
     { 
      DoSomething(); 
      ... 
      isSuccess = response.IsOk; // I put a breakpoint here 
      autoEvent.Set(); 
     } 
    }); 
    autoEvent.WaitOne(); 
    return isSuccess; // I also put a breakpoint here 
}