Question

我有一个httpWebRequest来访问XML并将其保存在本地然后读取并显示在屏幕上。问题是，我必须为多个“枢轴项”执行此操作，并且保存xml的方法是

private static void GetResponseCallback(IAsyncResult asynchronousResult)

并且不支持向其添加新变量，因此我可以动态命名xml（“tmp”+ xmlName +“。xml”）。

所以问题是：如何在xml名称中推送变量？

public class HttpWebReqMethod
    {

        public void httpRequestMethod (string url, string xmlName)
        {     
            HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(url);
            httpRequest.ContentType = "text/xml";
            httpRequest.Method = "POST";

            httpRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), httpRequest);
        }

        private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
        {
            HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;

            // End the operation
            Stream postStream = httpRequest.EndGetRequestStream(asynchronousResult);


            string postData = "";

            // Convert the string into a byte array.
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);

            // Write to the request stream.
            postStream.Write(byteArray, 0, postData.Length);
            postStream.Close();

            // Start the asynchronous operation to get the response
            httpRequest.BeginGetResponse(new AsyncCallback(GetResponseCallback), httpRequest);
        }

        private static void GetResponseCallback(IAsyncResult asynchronousResult)
        {
            HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;

            // End the operation
            HttpWebResponse response = (HttpWebResponse)httpRequest.EndGetResponse(asynchronousResult);
            Stream streamResponse = response.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            string responseStream = streamRead.ReadToEnd();

            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (var istream = new IsolatedStorageFileStream(@"tmp" + xmlName + ".xml", FileMode.OpenOrCreate, store))
                {
                    using (var sw = new StreamWriter(istream))
                    {
                        sw.Write(responseStream);
                    }
                }
            }

            // Close the stream object
            streamResponse.Close();
            streamRead.Close();

            // Release the HttpWebResponse
            response.Close();
        }

Answer 1

您可以做以下两件事：

使GetResponseCallback不是静态的，将xmlName存储在实例变量中
向请求传递状态对象（任何具有名为xmlName的属性，以及其他可识别的属性的东西），您可以从AsyncState

将GetResponseCallback的功能更改为以下内容，并将整个内容设为回调“工厂”

private static AsyncCallback GetResponseCallback(string xmlName)
 {
    return (IAsyncResult asynchronousResult) =>{
    HttpWebRequest httpRequest = (HttpWebRequest)asynchronousResult.AsyncState;
    // End the operation
    HttpWebResponse response = (HttpWebResponse)httpRequest.EndGetResponse(asynchronousResult);
    Stream streamResponse = response.GetResponseStream();
    StreamReader streamRead = new StreamReader(streamResponse);
    string responseStream = streamRead.ReadToEnd();

    using (var store = IsolatedStorageFile.GetUserStoreForApplication())
    {
        using (var istream = new IsolatedStorageFileStream(@"tmp" + xmlName + ".xml", FileMode.OpenOrCreate, store))
        {
            using (var sw = new StreamWriter(istream))
            {
                sw.Write(responseStream);
            }
        }
    }

    // Close the stream object
    streamResponse.Close();
    streamRead.Close();

    // Release the HttpWebResponse
    response.Close();
  }
}

编辑添加：
然后用法改为

 httpRequest.BeginGetRequestStream(GetRequestStreamCallback(xmlName), httpRequest);

Answer 2

这是一个映射到特定委托类型的回调方法，所以不，你不能修改它的签名。

解决此问题的一个选择是拥有一个单独的类，例如：

class HttpRequestState {
    HttpWebRequest httpWebRequest;
    string xmlFileName;
}

然后，您可以在运行Begin回调时将该类的实例设置为状态对象：

httpRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), httpRequest);

会改为

httpRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), new HttpRequestState() { httpWebRequest = httpRequest; xmlFileName = "tmp"+xmlName+".xml" });

然后，当然，您可以像这样提取xmlFileName 和 httpWebRequest：

HttpRequestState stateObj = (HttpRequestState)asynchronousResult.AsyncState;
HttpWebRequest httpRequest = stateObj.httpWebRequest;
string fileName = xmlFileName;

将变量推送到方法中

2 个答案: