Downloading .xls file with Response.WriteFile downloads file with webpage content

问题

I have a simple ASP.NET webpage using VB with a file upload control. The user will upload a .xls and a new .xls file is created in the project directory with a new format and some calculations. This file saves, opens, and displays without an issue.

Within this button click event, I want the newly-created file to download to the user's browser/Downloads folder. When using Response.WriteFile with a Response.End, the .xls file downloads properly...BUT there's a thread abort exception that is caught and nothing after the Response.WriteFile line is processed even if I put it in the catch statement (i.e. I have a label that I want to tell the user to then display that the file has been successfully downloaded).

Here's the initial code that mostly works:

Protected Sub btnUpload_Click(sender As Object, e As EventArgs) Handles btnUpload.Click
        If fuReport.HasFile Then

'All report processing occurs & report is created without issue

    Try
        Response.Clear()
        Response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}", strReportName))
        Response.ContentType = "application/vnd.ms-excel"
        'Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
        Response.WriteFile(strReportName)
        Response.End()
        lblResult.Text = "Report was successfully downloaded."
     Catch
        lblResult.Text = "Testing1."
     Finally
        lblResult.Text = "Testing2."
        fuReport = New FileUpload()
     End Try
    End If
    End Sub

I've seen some different recommendations for the ContentType of .xls files. Both of the content types above will download the file but nothing in the Catch or Finally statement is processed. lblResult still reads, "Please wait while your report is processing..."

I found online that the issue lies with Response.End(). Per https://support.microsoft.com/en-us/kb/312629/en-us, I replaced this with

HttpContext.Current.ApplicationInstance.CompleteRequest()

This caused a new issue. My .xls file would download, but it seemed to display gibberish, followed by some of the aspx page content. Here, the label is correctly listed even though it has not changed on the webpage. I don't have enough reputation to include a screenshot, but this is some of what the Excel file displays:

ˆdQ_9€`Èb/ecÈ¢l†=gÊC\Œ¬ÀxbY”Â…‘#ˆ,ör6ˆ,Ê…8ëY8ÖæBô?³2º‹CÓž€|^î¯{{<xJñ¯ªç2,FÑ+sbŸ£å›q³žcm"9ŸÛÆ…îâpoŸûñä_õ¥1­K×Ê1Ü–‘äŒä‚$‹’,ÊÞÿ?ëY9ÖÎɺa 9†7(Æ‘E‰c<µŠ$wïå¼Q9çƒìù93vì£Þ¾ŠõXè.î·ÛúÏöX;`>¸w!‚™•ó‘#Ž,8²(ãÞqÖ3q¬M¥dÝ ‚Â7VE¾‰`|mä^@Y”°çÞÌØZXß²‹O•½në›×å­=än½‘°i”EàqÅ^Ê6‹²(×›õìks   žú¦¸Ð½µW§îo[‚‡ÚGÈýz3·!dÑ„@ dq€E9õ×3lfl%Ø™^Vv
@ÈB{)[²èïmÖ³l¬…8óI–½-?o{ÖΤ,÷IJhC ²ØKÙ²hmïÕΞâ}û‡.vÝÌznµ³ð±Lâc¹7†E  ÜOpÁÅ^ÎÆEyüæ=£ÆÚÄÏnïýúº·7åå‡v³Í[;οŠþ•PˆÃp%*0B!ö
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<!DOCTYPE html> 

<html xmlns="http://www.w3.org/1999/xhtml"> 
<head id="Head1"><title>    

</title>    
    <script type="text/javascript"> 
        function changeLabel(){ 
            document.getElementById("lblResult").innerHTML = "Please wait while your report is processed...";   
        }   
    </script>   
</head> 
<body>  

    <form method="post" action="Uploader.aspx" id="form1" enctype="multipart/form-data">    
<div class="aspNetHidden">  
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="+yve+0TnTzr8dZbqET3gRkZx/Pw9iGFmDqDyyfeTPMoXlPTPVgX3FrRUhTd3lBZE0DkzyUKzhXOi6MqTdxe1jnYL+mdzQiyoaM5w5cv9vij3X1xtsW8P1zACrDj6IqUK87n3GcwFtdHCCblAdgFI8nPQZsJnRv9w8lNIurcrbfad534ICOt8S/++vRi9+s91DFi3woIbFMyxw3rvbUPQwg==" />    
</div>  

<div class="aspNetHidden">  

    <input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="C153B6F1" />
    <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="c3fKPUwILazJv1aW60quCxYtkspAHgetjdwMb7ugaEBN7qnUTTL7SrAVizVMaqXPAPqmyhDV0rtT1upkWYH9eOzqHjjmjvr9ZHty08BHB9OD/fCIuF8ExZbOqpiXOdGA" />


 </div> 


  <div> 
        <input type="file" name="fuReport" id="fuReport" style="width:306px;" />    
        <br />  
        <span id="lblResult">Report was successfully downloaded.</span> 
        <br />          
        <input type="submit" name="btnUpload" value="Upload" onclick="changeLabel();" id="btnUpload" /> 
    </div>      
    </form> 
</body> 
</html> 

I then tried replace all of the Response code with HTTPContext as shown here:

HttpContext.Current.Response.ClearContent()
HttpContext.Current.Response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}", strReportName))
HttpContext.Current.Response.ContentType = "application/vnd.ms-excel"
HttpContext.Current.Response.Write(strReportName)
HttpContext.Current.ApplicationInstance.CompleteRequest()

This also downloads a .xls file but with a graphical representation of the webpage. Again, I cannot post a picture, but the Excel file opens to show the button with text, Upload & says:

Report was successfully downloaded.

I have researched this for HOURS with no solution. I have tried pulling this particular code out of the try/catch/finally as someone else had success with but this did not help either.

Does anybody know how I can properly have the browser download the .xls file with the actual contents of my NewReport instead of it containing information from the aspx page??

回答1:

I like to use BinaryWrite, something like this:

Dim ms As New IO.MemoryStream
xWB.Write(ms)
Dim bytes As Byte() = ms.ToArray
Response.ContentType = "application/vnd.ms-excel"
Response.AddHeader("content-disposition", "attachment;filename=" & strReportName)
Response.BinaryWrite(bytes)
Response.Flush()
Response.End()

回答2:

I gave up on the idea of doing both processes automatically. I added in a Download button that only becomes visible once the report has been successfully processed. On the Download button's on click event, I have the excel file download. It's one more click than I wanted, but it gets the job done.

Protected Sub btnUpload_Click(sender As Object, e As EventArgs) Handles btnUpload.Click
If fuReport.HasFile Then
    Try        
        'All report processing occurs & report is created without issue   
        lblResult.Text = "Report was successfully processed."
        btnDownload.Visible = True  
    Catch
        lblResult.Text = "An error occurred. Please try again."
    Finally
        fuReport = New FileUpload()
    End Try
  Else
        lblResult.Text = "Please select a report to upload."
    End If
End Sub

Protected Sub btnDownload_Click(sender As Object, e As EventArgs) Handles btnDownload.Click
        Response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}", strReportName))
        Response.ContentType = "application/vnd.ms-excel"
        Response.WriteFile(strReportName)
        Response.End()
    End Sub
End Class

来源：https://stackoverflow.com/questions/31054275/downloading-xls-file-with-response-writefile-downloads-file-with-webpage-conten