Modifying the response object for creating and downloading a document

Question

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

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.ClearContent();
 response.ContentType = MimeMapping.GetMimeMapping(fileName);
 response.AddHeader("content-disposition",
 String.Format("attachment; filename={0}", fileName));
 response.BinaryWrite(data);
 response.End();
}

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.