I've been looking at some code done in C# ASP .NET WebForms and for some reason I really don't like the below code. What is the best alternative for creating a document and downloading it in Webforms, on the click of a button? Should the developer be messing with the Response at all, in this way?

Response.BufferOutput = true;
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("content-disposition", string.Format("attachment; filename={0:yyyyMMdd}.xlsx", DateTime.Now));

1 Answer 1


Yes, in ASP.NET WebForms you don't have any nice helper method to hide this. However if you do it often you should make it easier and less error-prone.

public static void WriteDownload(this HttpResponse response, string fileName, byte[] data)
    if (String.IsNullOrWhiteSpace(fileName))
        throw new ArgumentException("File name must be specified.", "fileName");

    if (data == null)
        throw new ArgumentNullException("data");


    response.ContentType = MimeMapping.GetMimeMapping(fileName);
        String.Format("attachment; filename={0}", fileName));


It will then be used like this:

Response.WriteDownload(GetFileNameFromTodayDate(".xlsx"), pkg.GetAsByteArray());

Where GetFileNameFromTodayDate() is simply:

private static string GetFileNameFromTodayDate(string extension)
    return String.Format("{0:yyyyMMdd}.{1}",
        DateTime.Now, extension.TrimStart(' ', '.');

Few more notes:

  • BufferOutput is true by default, you do not need to repeat it. However I'd consider to set it to false.
  • If you're using .NET Framework 4.5+ you do not need any function to resolve MIME type otherwise you'd better to resort some helper function but do not hard-code it anywhere.
  • You do not need Response.Flush() because buffering is on and, moreover, you do not stream anything else before Response.End(), it's just redundant.

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