需要帮助在 c# 中同步控制事件处理程序

Question

我有如下代码片段：

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
}

Communication函数原型如下：

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

其中 WebSocketIn 和 WebSocketOut 是两个委托。问题是当我调试程序时，"return isSuccess;" 语句在收到来自 "response.IsOk" 的结果之前总是运行所以该函数的 returned 值总是 "false"。也就是说，执行顺序是：

return 成功
isSuccess = response.IsOk（在 MessageReceived(WebSocket4Net) 事件触发后）

我不知道如何运行倒序。任何意见、建议或帮助将不胜感激。

谢谢

Answer 1

您可以使用async/await and 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 AutoResetEvent 等待异步功能完成。

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
}

需要帮助在 c# 中同步控制事件处理程序

Need help controlling event handler synchronously in c#

c#

lambda

multithreading

delegates

sync