C# Post Json数据的具体代码如下：

public string Post(string Url, string jsonParas)
{
string strURL = Url;

//创建一个HTTP请求
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(strURL);
//Post请求方式
request.Method = "POST";
//内容类型
request.ContentType = "application/x-www-form-urlencoded";

//设置参数，并进行URL编码

string paraUrlCoded = jsonParas;//System.Web.HttpUtility.UrlEncode(jsonParas);

byte[] payload;
//将Json字符串转化为字节
payload = System.Text.Encoding.UTF8.GetBytes(paraUrlCoded);
//设置请求的ContentLength
request.ContentLength = payload.Length;
//发送请求，获得请求流

Stream writer;
try
{
writer = request.GetRequestStream();//获取用于写入请求数据的Stream对象
}
catch (Exception)
{
writer = null;
Console.Write("连接服务器失败!");
}
//将请求参数写入流
writer.Write(payload, 0, payload.Length);
writer.Close();//关闭请求流

String strValue = "";//strValue为http响应所返回的字符流
HttpWebResponse response;
try
{
//获得响应流
response = (HttpWebResponse)request.GetResponse();
}
catch (WebException ex)
{
response = ex.Response as HttpWebResponse;
}

Stream s = response.GetResponseStream();

Stream postData = Request.InputStream;
StreamReader sRead = new StreamReader(s);
string postContent = sRead.ReadToEnd();
sRead.Close();

return postContent;//返回Json数据
}

　　//接收
　　//获取post过来的json数据结构
　　Stream postData = Request.InputStream;
　　StreamReader sRead = new StreamReader(postData);
　　string postContent = sRead.ReadToEnd();
　　sRead.Close();