这里讲的是服务代理，应用情景如下：
 A站点有一个JS脚本需要调用B站点的服务接口，但是A站点和B站点不是同一个域名下，这样就关系到跨域访问的了问题了，一种解决方法是通过一个代理去接管所有对B站点服务的调用。
服务器端：AcrossServer.ashx

public class AcrossServer : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";string clientKey = context.Request["ClientKey"];
        string clientIP = context.Request["ClientIP"];

        context.Response.Write(

代理服务：

public class AcrossClient : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";//构造Post数据
        string clientKey = "af8b908b-7735-4db6-9d8f-eef05b2eef69";
        string clientIP = context.Request.UserHostAddress;
        StringBuilder sb = new StringBuilder();
        sb.AppendFormat("ClientKey={0}&ClientIP={1}", clientKey, clientIP);
        foreach (string key in context.Request.Form.AllKeys)
        {
            sb.AppendFormat("&{0}={1}", key, context.Request.Form[key]);
        }
        string postData = sb.ToString();
        byte[] data = Encoding.UTF8.GetBytes(postData);//HttpWebRequest
        string url = string.Format("http://my2.csdn.net/Samples/CJB3/AcrossServer.ashx");
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = data.Length;
        request.Timeout = 10000;//10s

        string content = string.Empty;
        try
        {
            //把postdata写入HttpWebRequest
            using (Stream requestStream = request.GetRequestStream())
            {
                requestStream.Write(data, 0, data.Length);
                requestStream.Close();
            }
            //获取HttpWebResponse
            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    using (Stream stream = response.GetResponseStream())
                    {
                        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                        {
                            content = reader.ReadToEnd();
                            reader.Close();
                        }
                        stream.Close();
                    }
                }
                response.Close();
            }
        }
        catch (System.Net.WebException)
        {
            //TODO:考虑在此添加超时异常的日志
        }
        finally
        {
            if (request != null)
            {
                request.Abort();
                request = null;
            }
        }
        
        context.Response.Write(string.Format("AcrossClient=>{0}", content));
    }

}

我们通过在代理端重新封装所有的Post数据并且添加新的服务验证等数据一起Post到真正的服务接口，最后把调用的返回也返回给代理调用方。

当然，我们可以对Post操作进一步封装到一个方法

PostRequest