asp.net 文件下載，同樣適用於mvc

private void DownLoadFile(string fileName)
    {  
        string filePath = Server.MapPath(".") + "\\" + fileName;
        if (File.Exists(filePath))
        {
            FileInfo file = new FileInfo(filePath);
            Response.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8"); //解決中文亂碼
            Response.AddHeader("Content-Disposition", "attachment; filename=" + Server.UrlEncode(file.Name)); //解決中文文件名亂碼    
            Response.AddHeader("Content-length", file.Length.ToString());
            Response.ContentType = "appliction/octet-stream";
            Response.WriteFile(file.FullName);
            Response.End();
        }