url:为请求地址
postData:请求内容例如："key1=value1&key2=value2&key3=value3"

public static string PostUrl(string url, string postData)
{
string result = "";
try
{
ServicePointManager.Expect100Continue = false;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.ServicePoint.Expect100Continue = false;//指定此属性为false
request.Method = "POST";
request.ContentType = "application/json";
requestStream = request.GetRequestStream();
streamWriter = new StreamWriter(requestStream, Encoding.GetEncoding("utf-8"));
streamWriter.Write(jsonData);
streamWriter.Flush();
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
responseStream = response.GetResponseStream();
streamReader = new StreamReader(responseStream, Encoding.GetEncoding("utf-8"));
//获取响应内容
using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
{
result = reader.ReadToEnd();
}
} catch(Exception e){}
return result;
}