如何使用webclient发布body x-www-form-urlencoded？

using System.Net;
using System.Text;

WebClient client = new WebClient();

client.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";

string postData = "param1=value1&param2=value2";

byte[] byteArray = Encoding.UTF8.GetBytes(postData);

byte[] responseArray = client.UploadData(url, "POST", byteArray);
string response = Encoding.UTF8.GetString(responseArray);