Row Command in GridView

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C#3.0

C#

I have a gridview to display and download files.But when i click on the download button nothing happens..the gridview is:

<asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False"
            BackColor="White" BorderColor="#3366CC" BorderStyle="None" BorderWidth="1px"
            CellPadding="4" PageIndex="5" PageSize="5"
        style="margin-left: 312px; margin-top: 20px;" HorizontalAlign="Justify"
        onselectedindexchanged="GridView2_SelectedIndexChanged">
            <Columns>
                <asp:BoundField DataField="File_Name" HeaderText="File Name"
                    SortExpression="File_Name" />
                <asp:BoundField DataField="Document_Number" HeaderText="Document Number"
                    SortExpression="Document_Number" />
                <asp:BoundField DataField="Upload_Date" HeaderText="Uploaded On"
                    SortExpression="UploadDate" />
                <asp:BoundField DataField="Upload_User" HeaderText="Uploaded BY"
                    SortExpression="Upload_User" />
                <asp:ButtonField ButtonType="Link" CommandName="Dwn" Text="Download"
                    HeaderText="Download Files"/>
            </Columns>
            <FooterStyle BackColor="#99CCCC" ForeColor="#003399" />
            <HeaderStyle BackColor="#003399" Font-Bold="True" ForeColor="#CCCCFF" />
            <PagerStyle BackColor="#99CCCC" ForeColor="#003399" HorizontalAlign="Left" />
            <RowStyle BackColor="White" ForeColor="#003399" />
            <SelectedRowStyle BackColor="#009999" Font-Bold="True" ForeColor="#CCFF99" />
            <SortedAscendingCellStyle BackColor="#EDF6F6" />
            <SortedAscendingHeaderStyle BackColor="#0D4AC4" />
            <SortedDescendingCellStyle BackColor="#D6DFDF" />
            <SortedDescendingHeaderStyle BackColor="#002876" />
        </asp:GridView>

and the rowcommad is

protected void GridView2_RowCommand(object sender, GridViewCommandEventArgs e)

    {

       if (e.CommandName == "Dwn")
       {
           string path = ("NewFolder1") + "\\" +ddcollege.SelectedValue + "\\" + dddept.SelectedValue + "\\"
                         +ddcategory.SelectedValue + "\\" + ddloctn.SelectedItem + "\\";

            int index = Convert.ToInt32(e.CommandArgument);

           GridViewRow row = GridView2.Rows[index];

           string fName = row.Cells[1].Text;

           Response.ContentType = "application/octet-stream";

            Response.AddHeader("Content-Disposition", "attachment;filename=" + fName);

          Response.TransmitFile(Server.MapPath(path+ fName));

            Response.End();


       }


    }

any idea as to y.I even tried to debug it but upon clicking the button..the lines are not reached.

Thanks