如何保存一张网页上的图片（C#）到本地计算机上

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

namespace mynamespace
{
    public class Downloader
    {
        /// <summary>
        /// 下载图片
        /// </summary>
        /// <param name="picUrl">图片Http地址</param>
        /// <param name="savePath">保存路径</param>
        /// <param name="timeOut">Request最大请求时间，如果为-1则无限制</param>
        /// <returns></returns>
        public static bool DownloadPicture(string picUrl, string savePath,int timeOut)
        {
            bool value = false;
            WebResponse response = null;
            Stream stream = null;
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(picUrl);
                if (timeOut != -1) request.Timeout = timeOut;
                response = request.GetResponse();
                stream = response.GetResponseStream();
                if (!response.ContentType.ToLower().StartsWith("text/"))
                    value = SaveBinaryFile(response, savePath);
            }
            finally
            {
                if(stream!=null) stream.Close();
                if (response != null) response.Close();
            }
            return value;
        }
private static bool SaveBinaryFile(WebResponse response, string savePath)
        {
            bool value = false;
            byte[] buffer = new byte[1024];
            Stream outStream = null;
            Stream inStream = null;
            try
            {
                if (File.Exists(savePath)) File.Delete(savePath);
                outStream = System.IO.File.Create(savePath);
                inStream = response.GetResponseStream();
                int l;
                do
                {
                    l = inStream.Read(buffer, 0, buffer.Length);
                    if (l > 0) outStream.Write(buffer, 0, l);
                } while (l > 0);
                value = true;
            }
            finally
            {
                if(outStream!=null) outStream.Close();
                if(inStream!=null) inStream.Close();
            }
            return value;
        }
    }
}