c# - C#：在 C# 4.5 中等待请求完成

Question

我的asp.net 4.0 应用程序中有一个http 请求。我希望线程在继续之前等待。

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 responseBody 任务上调用 .Wait()

Answer 2

在 4.5 中（你的标题是这样说的）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
}

要下载字符串，您可以简单地使用

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

    MessageBox.Show(responseStr);

}

Answer 3

一种选择是调用 .Wait() 但更好的选择是使用 async

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

这可以使用async 关键字和await 关键字来完成，如下所示：

// 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 ...

}

请注意，await 关键字不会阻塞线程。相反，在异步方法的其余部分排队之后，控制权将返回给调用者，以便它可以继续处理。如果您需要调用者MyMethod()也等到 client.GetAsync() 完成，那么您最好使用同步调用。