利用 Response 输出文件

StringBuilder sb = new StringBuilder();

for (int i=1; i<=500000; i++)
{
    sb.Append(string.Format("{0} {1:D5}\r\n", DateTime.Now, i));
}

Response.AddHeader("Content-Disposition", "attachment; filename=test.txt");
Response.ContentType = "application/text";
Response.ContentEncoding=System.Text.Encoding.GetEncoding("GB2312");
Response.Write(sb);
Response.End();