getting datarow vales in gridview error - asp.net

Question

I have the following aspx code;
<asp:GridView ID="GridView1" runat="server" AllowPaging="True"
AllowSorting="True" AutoGenerateColumns="False" DataKeyNames="ProductId"
DataSourceID="edsinventory" OnRowCommand="GridView1_RowCommand"
ShowFooter="true" CssClass="mGrid">
<Columns>
<asp:TemplateField ShowHeader="False">
<EditItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="True"
CommandName="Update" Text="Update"></asp:LinkButton>
<asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False"
CommandName="Cancel" Text="Cancel"></asp:LinkButton>
</EditItemTemplate>
<FooterTemplate><asp:LinkButton ID="LinkButton3" runat="server" CommandName="Insert">Insert</asp:LinkButton></FooterTemplate>
<ItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False"
CommandName="Edit" Text="Edit"></asp:LinkButton>
<asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False"
CommandName="Delete" Text="Delete"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Id" InsertVisible="False"
SortExpression="Id">
<EditItemTemplate>
<asp:Label ID="lblEditId" runat="server" Text='<%# Eval("Id") %>'></asp:Label>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="lblId" runat="server" Text='<%# Bind("Id")%>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="ProductId" SortExpression="ProductId">
<EditItemTemplate>
<asp:TextBox ID="tbProdId" Width="50" runat="server" Text='<%# Bind("ProductId")%>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="tbInsertProdId" Width="50" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblProdId" runat="server" Text='<%# Bind("ProductId")%>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
'shortened for brevity
</Columns>
</asp:GridView>
here is the code behind
Protected Sub GridView1_RowCommand(sender As Object, e As GridViewCommandEventArgs)
' This just provides easier access to the Cells in the GridView
Dim cells = GridView1.FooterRow.Cells
Dim ctx As New teckEntities()
Dim addInventory As New inventory()
If e.CommandName = ("Insert") Then
'Create new Inventory object
addInventory.ProductId = Convert.ToInt32(DirectCast(cells(3).FindControl("tbInsertProdId"), TextBox).Text)
addInventory.Quantity = Convert.ToInt32(DirectCast(cells(4).FindControl("tbInsertQuantity"), TextBox).Text)
addInventory.Location = Convert.ToString(DirectCast(cells(1).FindControl("tbInsertLocation"), TextBox).Text)
'attach the fields to the inventory context
' note: Id autoincrements and doesn't need to be set manually
InsertInventoryItem(addInventory)
'need to call a gridview refresh here
GridView1.DataBind()
ElseIf e.CommandName = "Delete" Then
**addInventory.Id = Convert.ToInt32(DirectCast(cells(3).FindControl("lblEditId"), Label).Text)**
DeleteInventoryItem(Convert.ToInt32(addInventory.Id))
GridView1.DataBind()
End If
End Sub
I am getting the following error on the deleting routine where the **, why? The insert function works the same way and works properly.
Object reference not set to an instance of an object.

Answer 1

I think the problem is you're looking the Label lblEditId in Footer controls:
Dim cells = GridView1.FooterRow.Cells
...
addInventory.Id = Convert.ToInt32(DirectCast(cells(3).FindControl("lblEditId"), Label).Text)
Try this instead:
Update your delete linkbutton to (add the ID to the CommandArgument):
<asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False" CommandName="Delete" CommandArgument='<%#Eval("Id")%>' Text="Delete"></asp:LinkButton>
Then, replace your ** code with this:
Note: Based on the code you provided, it seem like the lblEditId is in column 2 hence the Cell(1) - zero based index, instead of Cell(3).
addInventory.Id = Convert.ToInt32(DirectCast(GridView1.Rows(e.CommandArgument).Cells(1).FindControl("lblEditId"), Label).Text)