C#请求Http地址

using System;
using System.IO;
using System.Net;
using System.Text;

public class HttpUtil
{

    private const string sContentType = "application/x-www-form-urlencoded";
    private const string sUserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

    public static string Send(string data, string url)
    {
        return Send(Encoding.GetEncoding("UTF-8").GetBytes(data), url);
    }

    public static string Send(byte[] data, string url)
    {
        Stream responseStream;
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        if (request == null)
        {
            throw new ApplicationException(string.Format("Invalid url string: {0}", url));
        }
        // request.UserAgent = sUserAgent;  
        request.ContentType = sContentType;
        request.Method = "POST";
        request.ContentLength = data.Length;
        Stream requestStream = request.GetRequestStream();
        requestStream.Write(data, 0, data.Length);
        requestStream.Close();
        try
        {
            responseStream = request.GetResponse().GetResponseStream();
        }
        catch (Exception exception)
        {
            throw exception;
        }
        string str = string.Empty;
        using (StreamReader reader = new StreamReader(responseStream, Encoding.GetEncoding("UTF-8")))
        {
            str = reader.ReadToEnd();
        }
        responseStream.Close();
        return str;
    }
}