.NET发送请求，携带json数据

/// <summary>
/// 发送请求
/// </summary>
/// <param name="Uri">请求地址</param>
/// <param name="JsonStr">json数据</param>
/// <returns></returns>
public static string ClientRequest(string Uri, string JsonStr)
{
try
{
string serviceAddress = Uri;
var httpRequest = (HttpWebRequest)HttpWebRequest.Create(serviceAddress);
httpRequest.Method = "POST";
httpRequest.ContentType = "application/json";
httpRequest.Proxy = null;
//httpRequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0) Gecko/20100101 Firefox/11.0";
httpRequest.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13";
httpRequest.Headers.Add("Accept-Language", "zh-cn,en-us;q=0.8,zh-hk;q=0.6,ja;q=0.4,zh;q=0.2");
httpRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
using (var dataStream = new StreamWriter(httpRequest.GetRequestStream()))
{
dataStream.Write(JsonStr);
dataStream.Flush();
dataStream.Close();
}

var httpResponse = (HttpWebResponse)httpRequest.GetResponse();
using (var dataStream = new StreamReader(httpResponse.GetResponseStream()))
{
var result = dataStream.ReadToEnd();
return result;
}
}
catch (Exception ex)
{
return "{\"error\":\"" + ex.Message + "\"}";
}
}