File not downloading from GridView on click event

Question

I have a GridView named gvEmplAttachments that has 3 columns:

id
FileName
FilePath

Each row has a LinkButton that will allows the user to download the file, that button is coded as such:

<asp:LinkButton  id="lbViewFile" runat="server" CommandName="ViewFile" CommandArgument='<%# Container.DataItemIndex %>' >View</asp:LinkButton>

The GridView is set with the following:

OnRowCommand ="gvEmplAttachments_OpenAttachment_RowCommand"

So that it will execute the function in the CodeBehind

In my CodeBehind I have this function:

protected void gvEmplAttachments_OpenAttachment_RowCommand(object sender, GridViewCommandEventArgs e)
{
    if (e.CommandName == "ViewFile")
    {
        //Get rowindex
        int rowindex = Convert.ToInt32(e.CommandArgument);
        //Get the Row
        GridViewRow gvr = gvUaSettings.Rows[rowindex];
        //Get the Needed Values
        Label lblPath = gvr.FindControl("lblFilePath") as Label;
        Label lblName = gvr.FindControl("lblFileName") as Label;
        //String The values
        string fileName = lblName.Text;
        string filePath = Server.MapPath(lblPath.Text);
        //Should Download the file
        System.Web.HttpResponse response = System.Web.HttpContext.Current.Response;
        response.ClearContent();
        response.Clear();
        response.ContentType = "application/x-unknown";
        response.AddHeader("Content-Disposition", "attachment; filename=" + fileName + ";");
        response.TransmitFile(filePath);
        response.Flush();
        response.End();
    }
}

But the problem is when I click the button I get this error:

Object reference not set to an instance of an object

My question is, what am I missing that would be causing the null value. Because the Grid is displaying the correct FileName and FilePath.

As you mentioned your **Gridview ID** is `gvEmplAttachments`, but the code you written to grab the row of Gridview which trigger **OnCommand** event is having different gridview ID `GridViewRow gvr = gvUaSettings.Rows[rowindex];` is this correct or code misplace? May it didn't get the proper Gridview Row. — Rojalin Sahoo, Sep 27 '17 at 06:33
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — VDWWD, Sep 27 '17 at 06:50
@Rojalin Sahoo good catch! that corrected the issue. - if you submit this as an answer I will mark it for you. — DebPepDevuan, Sep 27 '17 at 10:06

score 0 · Accepted Answer · answered Sep 27 '17 at 12:33

As you mentioned your Gridview ID is gvEmplAttachments, but the code you written to grab the row of Gridview which trigger OnCommand event is having different Gridview ID GridViewRow gvr = gvUaSettings.Rows[rowindex];.

You can try for the following Code to fetch the row triggering command event:

GridViewRow gvr = gvEmplAttachments.Rows[rowindex];

File not downloading from GridView on click event

1 Answers1