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asp.net – Opening excel files from the internet opens a blank excel window

Posted by: admin March 9, 2020 Leave a comment

Questions:

A method in dumping a GridView to an Excel file to download/open from the internet was recently broken with new Windows Updates.

My code dumps from a GridView to an XLS file using StringWriter, HTMLTextWriter and RenderControl. A common approach using the following code from http://www.aspsnippets.com/Articles/Export-GridView-to-Excel-in-ASPNet-with-Formatting-using-C-and-VBNet.aspx

Protected Sub ExportToExcel(sender As Object, e As EventArgs)
    Response.Clear()
    Response.Buffer = True
    Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.xls")
    Response.Charset = ""
    Response.ContentType = "application/vnd.ms-excel"
    Using sw As New StringWriter()
        Dim hw As New HtmlTextWriter(sw)

        'To Export all pages
        GridView1.AllowPaging = False
        Me.BindGrid()

        GridView1.HeaderRow.BackColor = Color.White
        For Each cell As TableCell In GridView1.HeaderRow.Cells
            cell.BackColor = GridView1.HeaderStyle.BackColor
        Next
        For Each row As GridViewRow In GridView1.Rows
            row.BackColor = Color.White
            For Each cell As TableCell In row.Cells
                If row.RowIndex Mod 2 = 0 Then
                    cell.BackColor = GridView1.AlternatingRowStyle.BackColor
                Else
                    cell.BackColor = GridView1.RowStyle.BackColor
                End If
                cell.CssClass = "textmode"
            Next
        Next

        GridView1.RenderControl(hw)
        'style to format numbers to string
        Dim style As String = "<style> .textmode { } </style>"
        Response.Write(style)
        Response.Output.Write(sw.ToString())
        Response.Flush()
        Response.[End]()
    End Using
End Sub

Public Overrides Sub VerifyRenderingInServerForm(control As Control)
    ' Verifies that the control is rendered
End Sub

Excel (2013) will open to a blank window, with no warning or message as to why anything was blocked, and without option to accept the file to open.

My code is run on an intranet site, and I do have access to group policies / settings / user configurations in Windows.

How to&Answers:

Solution 1

1) Open Excel Go to File Options

2) Click Trust Center -> Trust Center Settings

3) Go to Protected View. there are 3 options that show that were all clicked. Uncheck the first option that reads — “Enable Protected View for files originating from the Internet”. In some cases as reported in the comments below both the 1st and 2nd options need to be unchecked (Thanks @mosheb)

Solution 2

Uninstall these Windows Updates:

  • Windows Update KB3115262 (Excel 2013)
  • Windows Update KB3115130 (Excel 2010)

Answer:

Solution 3

  • Go into the properties of the file (R click – properties)
  • Click ‘Unblock’
  • Click ‘Apply’

Answer:

changing the security options was unfortunately not an option, but it turns out that if you export to CSV instead of XLS then the file will open in Excel ignoring the trust center stuff.

We’re in Classic ASP, so we change the page from exporting an HTML table format to CSV and changed our header and contenttype to this:

Response.AddHeader "content-disposition", "attachment; filename=search_results.csv"
Response.ContentType = "text/csv"

and did line breaks with: Response.Write (chr(10))

Answer:

Try doing following:

Replace “attachment” from

Response.AddHeader("content-disposition","attachment;filename=GridViewExport.xls")

with “inline”

Response.AddHeader("content-disposition","inline;filename=GridViewExport.xls")

It may help!

Content-Disposition:What are the differences between "inline" and "attachment"?

Answer:

Just thought I’d mention there is a third solution:

Add the site generating the .xls to your Trusted Sites list. I had to add about a dozen websites via GPO, because our CIO is refusing to roll back the KB… =(

Answer:

Per Raniel66’s suggestion, if the excel opens as blank even after adding the site to your Trusted Sites list, you may try/suggest below work around.

Open excel workbook even though it is grayed out/blank, then click on ‘View’ tab in the excel and then click on ‘full screen/maximize screen icon’ as shown in screen shot below. This is what worked for me.

enter image description here

Answer:

Having same issue. An update blocked this exporting to excel activity and not all of my world wide users have permissions to unblock. It affects 2010 and 2013 .xls. My thought it to address the Content type. Have you tried switching your Content Type from application/vnd.ms-excel to application/vnd.openxmlformats-officedocument.spreadsheetml.sheet and using xlsx instead?