异步方法的返回值

本文关键字：返回值 异步方法 | 更新日期: 2023-09-27 18:08:55

我有一个主页，在那里我调用一个类，用异步方法读取JSON，这个方法工作得很好，但我需要返回JSON的值到主页。

MainPage.cs, 

private void btnPrueba_Click(object sender, RoutedEventArgs e)
{

Dictionary<string,string> parametros = new Dictionary<string,string>();
parametros.Add("login", "12345678R");
parametros.Add("password", "123123");
objPrueba = new prueba();
objPrueba.doPost("http://prueba.es/login", parametros);
}
类Post.cs

, 

public void doPost(string url, Dictionary<string, string> parametros)
{
System.Uri myUri = new System.Uri(url);
HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(myUri);
myRequest.Method = "POST";
myRequest.ContentType = "application/x-www-form-urlencoded";
//relleno variable con los parametros
foreach (KeyValuePair<string, string> D in parametros)
{
parametrosData = parametrosData + D.Key + "=";
parametrosData = parametrosData + D.Value + "&";
}

bool a = myRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), myRequest).IsCompleted;
string b = "1231232";

}

void GetRequestStreamCallback(IAsyncResult callbackResult)
{
HttpWebRequest myRequest = (HttpWebRequest)callbackResult.AsyncState;
// End the stream request operation
Stream postStream = myRequest.EndGetRequestStream(callbackResult);
// Create the post data
string postData = parametrosData;
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Add the post data to the web request
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
// Start the web request


myRequest.BeginGetResponse(new System.AsyncCallback(GetResponsetStreamCallback), myRequest);
}
void GetResponsetStreamCallback(IAsyncResult callbackResult)
{
HttpWebRequest request = (HttpWebRequest)callbackResult.AsyncState;
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(callbackRe sult);
using (StreamReader httpWebStreamReader = new StreamReader(response.GetResponseStream()))
{
string result = httpWebStreamReader.ReadToEnd();
//For debug: show results
Debug.WriteLine(result);
//RETURN VALUE result TO MAINPAGE.CS

}
}

异步方法的返回值

您最好使用异步函数，这将使您的代码更简单。

你会有这样的东西:(抱歉格式不好，我还不熟悉的StackOverflow编辑器…)

public async Task<string> doPost(string url, Dictionary<string, string> parametros)
{
System.Uri myUri = new System.Uri(url);
HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(myUri);
myRequest.Method = "POST";
myRequest.ContentType = "application/x-www-form-urlencoded";
//relleno variable con los parametros
foreach (KeyValuePair<string, string> D in parametros)
{
parametrosData = parametrosData + D.Key + "=";
parametrosData = parametrosData + D.Value + "&";
}
Stream postStream = await myRequest.GetRequestStreamAsync();
// Create the post data
string postData = parametrosData;
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Add the post data to the web request
postStream.Write(byteArray, 0, byteArray.Length);
postStream.Close();
// Start the web request
HttpWebResponse response = await myRequest.GetResponseAsync();
string result;
using (StreamReader httpWebStreamReader = new StreamReader(response.GetResponseStream()))
{
 result = httpWebStreamReader.ReadToEnd();

//For debug: show results
Debug.WriteLine(result);
}
return result;
}

然后你可以简单地做:

private async void btnPrueba_Click(object sender, RoutedEventArgs e)
{

Dictionary<string,string> parametros = new Dictionary<string,string>();
parametros.Add("login", "12345678R");
parametros.Add("password", "123123");
objPrueba = new prueba();
string result = await objPrueba.doPost("http://prueba.es/login", parametros);
// You can use the string to update the GUI if you want, because this code is running on the GUI thread
}
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