asp.netvb.netexcelintranet

Opening excel files from the internet opens a blank excel window

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.

Solution

  • 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: