向post请求中写入数据，最终保存在了HttpWebRequest.Params中

protected void btnLogin_Click(object sender, EventArgs e)
{ string Url = "http://localhost:18472/DataRequest.aspx";
string contentType = "application/x-www-form-urlencoded";
string username = "administrator";
string password = "admin";
IDictionary<string,string> param=new Dictionary<string,string>();
param.Add("username",username);
param.Add("password",password);
int i = ;
StringBuilder sb=new StringBuilder();
foreach (var key in param.Keys)
{
if (i>)
{
sb.AppendFormat("&{0}={1}", key, param[key]);
}
else
{
sb.AppendFormat("{0}={1}", key, param[key]);
}
i++;
}
//string content = SendPost(sb.ToString(),Url,contentType);
string content = SendPost(username,Url,contentType);
}
/// <summary>
///
/// </summary>
/// <param name="data">写入流中的数据，最后将保存在request.params中，是Idictionary类型的变量；如果是没有等号的string类型，key=null，value=string</param>
/// <param name="url">请求的url</param>
/// <param name="contentType">请求的内容类型</param>
/// <returns></returns>
public static string SendPost(string data, string url, string contentType)
{
string content = string.Empty;
HttpWebRequest httpWebRequest = WebRequest.Create(url) as HttpWebRequest;
httpWebRequest.AllowAutoRedirect = true;
httpWebRequest.Method = "POST";
httpWebRequest.ContentType = contentType;
using (StreamWriter sw = new StreamWriter(httpWebRequest.GetRequestStream()))
{
sw.Write(data);
}
HttpWebResponse httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse;
using (StreamReader sr = new StreamReader(httpWebResponse.GetResponseStream(), System.Text.Encoding.Default))
{
content = sr.ReadToEnd();
}
//httpWebRequest.EndGetResponse;
return content;
}

string content="";
using (Stream stream = HttpContext.Current.Request.InputStream)
{
using (StreamReader sr = new StreamReader(stream, Encoding.UTF8))
{
content=sr.ReadToEnd();
}
}

string XML=content;
HttpContext context=HttpContext.Current;
context.Items.Add("XML", XML); 

string XML=context.Items["XML"].ToString();