求一个c#的 post请求 json 并且接收返回json数据的一个demo。

public string HttpPost(string url,string data)
{
HttpWebRequest request=(HttpWebRequest)WebRequest.Create(url);
request.ContentType="application/json";
request.Method="POST";
byte[] buffer=Encoding.UTF8.GetBytes(data);
using(Stream stream=request.GetRequestStream())
{
stream.Write(buffer,0,buffer.Length);
}
HttpWebResponse response=(HttpWebResponse)request.GetResponse();
string result=string.Empty;
using(StreamReader reader=new StreamReader(response.GetResponseStream()))
{
result=reader.ReadToEnd();
}
return result;
}