C#实现在winfrom程序中下载文件

//下载文件
//downlaodUrl  系统路径如：http://xxx.xxx.xxx/UpFile/kaoqin.doc
//fileName     自定义文件名字加后缀（如：考勤.doc）
//filePath     文件存放路径如： E：\2016\1\
public static void downfile(string downloadUrl,string filename,string filepath)
{
    HttpWebRequest hwr = (HttpWebRequest)WebRequest.Create(downloadUrl);
    hwr.Timeout = ;
    HttpWebResponse hwp = (HttpWebResponse)hwr.GetResponse();
    Stream ss = hwp.GetResponseStream();
    byte[] buffer = new byte[];
    if (!Directory.Exists(filepath))
    {
        Directory.CreateDirectory(filepath);
    }
    FileStream fs = new FileStream(
    string.Format(filepath + @"\" + filename),
    FileMode.Create);
    try
    {
        int i;
        while ((i = ss.Read(buffer, , buffer.Length)) >)
        {
        fs.Write(buffer, , i);
        }
        fs.Close();
        ss.Close();
    }
    catch (Exception)
    {
        throw;
    }
}