C# post请求 HttpWebRequest

//body是要传递的参数,格式"roleId=1&uid=2"
//post的cotentType填写:
//"application/x-www-form-urlencoded"
//soap填写:"text/xml; charset=utf-8"

public  string PostHttp(string url, string body, string contentType)

{

HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

httpWebRequest.ContentType = contentType;

httpWebRequest.Method = "POST";

httpWebRequest.Timeout = 20000;

byte[] btBodys = Encoding.UTF8.GetBytes(body);

httpWebRequest.ContentLength = btBodys.Length;

httpWebRequest.GetRequestStream().Write(btBodys, 0, btBodys.Length);

HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();

StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());

string responseContent = streamReader.ReadToEnd();

httpWebResponse.Close();

streamReader.Close();

httpWebRequest.Abort();

httpWebResponse.Close();

return responseContent;

}