異步方法的返回值

Question

我有一個主頁，在那裏我調用一個讀取JSON與異步方法的類，這種方法很好，但我需要返回JSON的值到主頁面。

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); 

} 

類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 



} 
} 

Answer 1

你最好使用異步功能，這將使你的代碼更簡單。

你會碰到這樣的：（對不起，壞的格式，我不是StackOverflow的編輯器既熟悉又......）

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; 
} 

然後，你可以簡單地做：

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 

}