C#保存网络图片到本地

#region 保存web图片到本地
    /// <summary>
    /// 保存web图片到本地
    /// </summary>
    /// <param name="imgUrl">web图片路径</param>
    /// <param name="path">保存路径</param>
    /// <param name="fileName">保存文件名</param>
    /// <returns></returns>
    public static string SaveImageFromWeb(string imgUrl, string path, string fileName)
    {
        if (path.Equals(""))
            throw new Exception("未指定保存文件的路径");
        string imgName = imgUrl.ToString().Substring(imgUrl.ToString().LastIndexOf("/") + 1);
        string defaultType = ".jpg";
        string[] imgTypes = new string[] { ".jpg", ".jpeg", ".png", ".gif", ".bmp" };
        string imgType = imgUrl.ToString().Substring(imgUrl.ToString().LastIndexOf("."));
        string imgPath = "";
        foreach (string it in imgTypes)
        {
            if (imgType.ToLower().Equals(it))
                break;
            if (it.Equals(".bmp"))
                imgType = defaultType;
        }

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(imgUrl);
        request.UserAgent = "Mozilla/6.0 (MSIE 6.0; Windows NT 5.1; Natas.Robot)";
        request.Timeout = 3000;

        WebResponse response = request.GetResponse();
        Stream stream = response.GetResponseStream();

        if (response.ContentType.ToLower().StartsWith("image/"))
        {
            byte[] arrayByte = new byte[1024];
            int imgLong = (int)response.ContentLength;
            int l = 0;

            if (fileName == "")
                fileName = imgName;

            FileStream fso = new FileStream(path + fileName + imgType, FileMode.Create);
            while (l < imgLong)
            {
                int i = stream.Read(arrayByte, 0, 1024);
                fso.Write(arrayByte, 0, i);
                l += i;
            }

            fso.Close();
            stream.Close();
            response.Close();
            imgPath = fileName + imgType;
            return imgPath;
        }
        else
        {
            return "";
        }
    }