Winform下载文件

/// <summary>/// 下载文件/// </summary>/// <param name="URL">下载文件地址</param>/// <param name="Filename">下载后的存放地址</param>/// <param name="Prog">用于显示的进度条</param>public void DownloadFile(string URL, string filename, System.Windows.Forms.ProgressBar prog){try{                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;if (prog != null){prog.Maximum = (int)totalBytes;}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();}catch (System.Exception){throw;}}/// <summary>/// 下载文件/// </summary>/// <param name="URL">下载文件地址</param>/// <param name="Filename">下载后的存放地址</param>public void DownloadFile(string URL, string filename){DownloadFile(URL, filename, null);}