winform从服务器下载文件怎么设置保存路径

[qq_35761136]

我的代码如下：
public void DownloadFile(string URL, string filename, System.Windows.Forms.ProgressBar prog)
{
System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL);
System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)Myrq.GetResponse();
long totalBytes = myrp.ContentLength;//获取请求返回的内容长度
if (prog != null)
{
prog.Maximum = (int)totalBytes;//将返回长度赋值给进度条控件
}
System.IO.Stream st = myrp.GetResponseStream();
System.IO.Stream so = new System.IO.FileStream(filename, System.IO.FileMode.Create);
long totalDownloadedByte = 0;
byte[] by = new byte[1024];
int osize = st.Read(by, 0, (int)by.Length);
while (osize > 0)
{
totalDownloadedByte = osize + totalDownloadedByte;
System.Windows.Forms.Application.DoEvents();
so.Write(by, 0, osize);
if (prog != null)
{
prog.Value = (int)totalDownloadedByte;
}
osize = st.Read(by, 0, (int)by.Length);
}
so.Close();
st.Close();
try
{

}
catch (System.Exception)
{
throw;
}
}
这个方法下载的路径是固定的，怎么改能保存至其他位置？或者最好让用户自己选择。