protected void Button1_Click(object sender, EventArgs e)
{
	//TransmitFile實現下載
	/*
	 微軟為Response物件提供了一個新的方法TransmitFile來解決使用Response.BinaryWrite
	 下載超過400mb的檔案時導致Aspnet_wp.exe程序回收而無法成功下載的問題。
	 程式碼如下：
	*/
	Response.ContentType = "application/x-zip-compressed";
	Response.AddHeader("Content-Disposition", "attachment;filename=test.txt");
	string filename = Server.MapPath("test.txt");
	Response.TransmitFile(filename);
	Response.Write("<script language=\"javascript\" type=\"text/javascript\">");
	Response.Write("alert(\"下載成功\");");
	Response.Write("window.location.href=\"test.aspx\";");
	Response.Write("</script>");

}
protected void Button2_Click(object sender, EventArgs e)
{
	//WriteFile實現下載
	string fileName = "testclient.txt";//客戶端儲存的檔名
	string filePath = Server.MapPath("test.txt");//路徑

	FileInfo fileInfo = new FileInfo(filePath);
	Response.Clear();
	Response.ClearContent();
	Response.ClearHeaders();
	Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
	Response.AddHeader("Content-Length", fileInfo.Length.ToString());
	Response.AddHeader("Content-Transfer-Encoding", "binary");
	Response.ContentType = "application/octet-stream";
	Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
	Response.WriteFile(fileInfo.FullName);
	Response.Flush();
	Response.End();

}
protected void Button3_Click(object sender, EventArgs e)
{
	//WriteFile分塊下載
	string fileName = "testclient.txt";//客戶端儲存的檔名
	string filePath = Server.MapPath("test.txt");//路徑
	System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
	if (fileInfo.Exists == true)
	 {
		const long ChunkSize = 409600;//100K 每次讀取檔案，只讀取100Ｋ，這樣可以緩解伺服器的壓力
		byte[] buffer = new byte[ChunkSize];

		 Response.Clear();
		 System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
		long dataLengthToRead = iStream.Length;//獲取下載的檔案總大小
		 Response.ContentType = "application/octet-stream";
		 Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
		while (dataLengthToRead > 0 && Response.IsClientConnected)
		 {
			int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//讀取的大小
			 Response.OutputStream.Write(buffer, 0, lengthRead);
			 Response.Flush();
			 dataLengthToRead = dataLengthToRead - lengthRead;
		 }
		 Response.Close();
	 }
 }

//字元流方式下載檔案
protected void Button4_Click(object sender, EventArgs e)
{
	string fileName = "testclient.txt";//客戶端儲存的檔名
	string filePath = Server.MapPath("test.txt");//路徑
	//以字元流的形式下載檔案
	FileStream fs = new FileStream(filePath, FileMode.Open);
	byte[] bytes = new byte[(int)fs.Length];
	fs.Read(bytes, 0, bytes.Length);
	fs.Close();
	Response.ContentType = "application/octet-stream";
	//通知瀏覽器下載檔案而不是開啟
	Response.AddHeader("Content-Disposition", "attachment;   filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
	Response.BinaryWrite(bytes);
	Response.Flush();
	Response.End();
}