将变量推送到方法中

本文关键字：方法 变量 | 更新日期: 2023-09-27 18:35:30

我有一个httpWebRequest来访问XML并将其保存在本地，然后读取它并将其显示在屏幕上。问题是，我必须为多个"透视项"执行此操作，而保存 xml 的方法为 

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();
        }

将变量推送到方法中

以下是您可以做的两件事：

  1. 使 GetResponseCallback 不是静态的，并将 xmlName 存储在实例变量中
  2. 将状态对象（具有名为 xmlName 的属性的任何内容，以及用于标识它的其他内容）传递给请求，您可以从 AsyncState

  3. 将 GetResponseCallback 的函数更改为以下内容，并使整个事情成为回调"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();
  }
}

编辑以添加：
然后，用法更改为

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

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。

解决此问题的一种选择是使用一个单独的类，如下所示：

class HttpRequestState {
    HttpWebRequest httpWebRequest;
    string xmlFileName;
}

然后，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);

将更改为

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

然后，当然，你可以像这样拉出xmlFileName和httpWebRequest：

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