c# – 使用async / await和System.Threading.Tasks.Parallel时出

public async Task ExecuteAsync()
{
     Task<IEnumerable<Comment>> gettingComments = RetrieveComments();

     Dictionary<string,ReviewManager> reviewers = ConfigurationFacade.Repositories.ToDictionary(name => name,name => new ReviewManager(name));

     IEnumerable<Comment> comments = await gettingComments;

     Parallel.ForEach(reviewers,(reviewer) => {
          Dictionary<Comment,RevisionResult> reviews = reviewer.Value.Review(comments);

          int amountModerated = ModerateComments(reviews.Where(r => r.Value.IsInsult),"hide");
     });
}

我的ModerateComments方法如下所示：

private Task<int> ModerateComments(IEnumerable<Comment> comments,string operation)
{
      return Task.Factory.StartNew(() =>
      {
          int moderationCount = 0;
          Parallel.ForEach(comments,async (comment) => 
          {
               bool moderated = await ModerateComment(comment,operation); //Problem here
               if(moderated)
                   moderationCount++;
          }
          return moderationCount;
      };
}

最后：

private async Task<bool> ModerateComment(Comment comment,string operation,string authenticationToken = null)
{
      if(comment == null) return false;

      if(String.IsNullOrWhiteSpace(authenticationToken))
             authenticationToken = CreateUserToken(TimeSpan.FromMinutes(1));

      string moderationEndpoint = ConfigurationFacade.ModerationEndpoint;

      using(HttpRequestMessage request = new HttpRequestMessage())
      {
          request.Method = HttpMethod.Post;
          request.RequestUri = new Uri(moderationEndpoint);
          using(HttpResponseMessage response = await _httpClient.SendAsync(request)) //Problem here
          {
               if(!response.IsSuccessStatusCode)
               {
                    if(response.StatusCode == HttpStatusCode.Unauthorized)
                        return await ModerateComment(comment,operation,null); //Retry operation with a new access token
                    else if(response.StatusCode == HttpStatusCode.GatewayTimeout)
                        return await ModerateComment(comment,authenticationToken); //Retry operation

                    return false;
               } 
          }
      }

      return true;
}

我在运行时遇到了一个奇怪的问题.以上所有代码都正常工作,除非它到达该行：

using(HttpResponseMessage response = await _httpClient.SendAsync(request)) {
      //...
}

当我调试我的应用程序时,执行该指令,但就在此之后,它不会抛出任何异常,也不会返回任何内容,它只是完成执行并且我被派生到Parallel.ForEach循环的下一个语句.

这很难解释所以我会发布一些图片：

到目前为止一切顺利,我到达以下代码行：

执行进展顺利,我接到了对Moderation API的调用

即使我在调试器中按F10(Next语句),执行流也会跳转到Parallel.ForEach循环中的下一个循环.

正如你所看到的,我在try-catch中有断点,只是抛出任何异常,但断点永远不会被激活,也不会激活if(moderacion)commentCount中的断点.

那么这里发生了什么？我的执行流程去了哪里？它只是在将POST请求发送到API后消失了.

继续执行后,可枚举中的所有元素都执行相同的跳转,因此,我的commentCount变量最终等于0