Null Reference error in gridview code

Question

While debugging I found that ItemID value is getting null. I am trying to get the list item's ID.

   ItemId = GridView1.DataKeys[e.RowIndex].Value.ToString();

Can anyone please tell me what could be the reason and how to solve this?

I have tried different things but nothing is working.

Is there anything wrong with this gridview?

<asp:GridView ID="GridView1" runat="server" OnRowEditing="Edit_row" OnRowCancelingEdit="cancel_Edit" OnRowDeleting="Delete_row" OnRowUpdating="Update_row" AutoGenerateColumns="true" AutoGenerateEditButton="true" AutoGenerateDeleteButton="true" BackColor="White" BorderColor="#DEDFDE" BorderStyle="None" BorderWidth="1px" CellPadding="4" ForeColor="Black" GridLines="Vertical" OnSelectedIndexChanged="GridView1_SelectedIndexChanged">
               <Columns>
                   <asp:TemplateField HeaderText="Sr No.">
                       <ItemTemplate>
                           <%# Container.DataItemIndex+1 %>
                       </ItemTemplate>
                   </asp:TemplateField>

               </Columns>

                 <AlternatingRowStyle BackColor="White" />
                <FooterStyle BackColor="#CCCC99" />
                <HeaderStyle BackColor="#6B696B" Font-Bold="True" ForeColor="White" />
                <PagerStyle BackColor="#F7F7DE" ForeColor="Black" HorizontalAlign="Right" />
                <RowStyle BackColor="#F7F7DE" />
                <SelectedRowStyle BackColor="#CE5D5A" Font-Bold="True" ForeColor="White" />
                <SortedAscendingCellStyle BackColor="#FBFBF2" />
                <SortedAscendingHeaderStyle BackColor="#848384" />
                <SortedDescendingCellStyle BackColor="#EAEAD3" />
                <SortedDescendingHeaderStyle BackColor="#575357" />
            </asp:GridView>

Answer 1

I guess you will need set DataKeyNames property of gridview. I don't see that property set in your Gridview.

Hence ItemId = GridView1.DataKeys[e.RowIndex].Value.ToString(); returning null value.

For reference: https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.datakeys(v=vs.110).aspx

https://msdn.microsoft.com/en-in/library/system.web.ui.webcontrols.gridview.datakeynames(v=vs.110).aspx