c# - 如何等待 UploadStringAsync 方法完成

Question

我正在尝试/想要等到异步任务完成，这就是我正在尝试做的

public class savetodbsingle 
{
    public static  string  insert(string id, string type, string cat)
    {
        Uri uri = new Uri("http://yxz.com");

        WebClient wc = new WebClient();
        wc.Headers[HttpRequestHeader.ContentType] = "application/json";
        wc.UploadStringAsync(uri, "POST", json);

        wc.UploadStringCompleted += wc_UploadComplete6;
    }

    private static   void wc_UploadComplete6(object sender, UploadStringCompletedEventArgs e)
    {
        //Saving to database logic here 
    }
}

从其他页面调用该方法

//calling method
savetodbsingle.insert(id,type,cat)); 

// i want to show messegebox from here when above task completes 
MessegeBox.Show("Completed");

那么如何实现呢？我曾尝试使方法异步然后等待它，但这没有帮助

Answer 1

改用 UploadStringTaskAsync 方法

这将返回一个您可以等待的任务。

https://msdn.microsoft.com/en-us/library/hh159423%28v=vs.110%29.aspx

 public static  async string  insert(string id, string type, string cat, Action<object,Exception> callback)
    {
         ----
        string result  = await wc.UploadStringTaskAsync(uri, "POST", json);

    }