C＃：等待一個請求在C＃4.5中完成

Question

我在我的asp.net 4.0應用程序中有一個http請求。我希望線程在繼續之前等待。

HttpClient client = new HttpClient(); 
HttpResponseMessage responseMsg = client.GetAsync(requesturl).Result; 

// I would like to wait till complete. 

responseMsg.EnsureSuccessStatusCode(); 
Task<string> responseBody = responseMsg.Content.ReadAsStringAsync(); 

Answer 1

在呼叫.Wait（）的responseBody任務

Answer 2

在4.5（你的標題是這麼說的），你可以使用async/await

public async void MyMethod() 
{ 
    HttpClient client = new HttpClient(); 
    HttpResponseMessage responseMsg = await client.GetAsync("http://www.google.com"); 

    //do your work 
} 

要下載一個字符串，你可以簡單地使用

public async void Question83() 
{ 
    HttpClient client = new HttpClient(); 
    var responseStr = await client.GetStringAsync("http://www.google.com"); 

    MessageBox.Show(responseStr); 

} 

Answer 3

一個選項是調用.Wait（），但更好的選擇是使用異步

public async void GetData() 
{ 
    using(HttpClient client = new HttpClient()) 
    { 
     var responseMsg = await client.GetAsync(requesturl); 
     responseMsg.EnsureSuccessStatusCode(); 
     string responseBody = await responseMsg.Content.ReadAsStringAsync(); 
    } 
} 

}

Answer 4

這可以通過使用async keyword和await keyword來完成，像這樣：

// Since this method is an async method, it will return as 
// soon as it hits an await statement. 
public async void MyMethod() 
{ 

    // ... other code ... 

    HttpClient client = new HttpClient(); 
    // Using the async keyword, anything within this method 
    // will wait until after client.GetAsync returns. 
    HttpResponseMessage responseMsg = await client.GetAsync(requesturl).Result; 
    responseMsg.EnsureSuccessStatusCode(); 
    Task<string> responseBody = responseMsg.Content.ReadAsStringAsync(); 

    // ... other code ... 

} 

請注意，關鍵字的await不會阻塞線程。相反，在異步方法的其餘部分排隊後，控制權將返回給調用者，以便繼續處理。如果您需要MyMethod()的調用者也等待client.GetAsync（）完成，那麼最好使用同步調用。