Templated Editable GridView Problem

[Frank]

Hello All,

I am working with VS.NET 2005 and I have an editable GridView whose HTML
markup is shown below.

In short, when the user clicks on the Edit button, one of the textboxes is
replaced with a DropDownList that displays account numbers in a list. If the
user selects an account from the DropDownList that already exists in the
list, I wish to hide the 'Update' button or column, along with displaying a
warning message. I try to do this with this code behind:
protected void CheckForDup(obj ect sender, EventArgs e)

{

int int_temp =
Convert.ToInt32 (listAdapter.Fi ndAccountInList (DDL_BlockList. SelectedValue,
((DropDownList) sender).Selecte dValue));

if (int_temp != 0)

{

GridView Temp = new GridView();

Temp = (GridView)Page. FindControl("GV _Accts");

Temp.Columns[0].Visible = false;
LBL_Warn.Text = "That Account Already Exists in the List!";

LBL_Warn.Visibl e = true;

}

else

{

LBL_Warn.Visibl e = false;

}

}

However, when it runs, I get an "Object reference not set to an instance of
an object." exception.

It doesn't like the line that reads 'Temp.Columns[0].Visible = false;'

Anyone have any suggestions please?

Thanks in advance

<asp:GridView ID="GV_Accts" runat="server" AutoGenerateCol umns="False"
DataKeyNames="I D"

DataSourceID="O bjectDataSource 2" OnRowUpdated="A djustUnitDispla y"
OnRowDeleted="A djustUnitDispla y" AllowPaging="Tr ue">

<Columns>

<asp:CommandFie ld ShowDeleteButto n="True" ShowEditButton= "True" />

<asp:TemplateFi eld HeaderText="Acc ount" SortExpression= "Account">

<EditItemTempla te>

<asp:DropDownLi st ID="DropDownLis t1" runat="server"
DataSourceID="D DL_Accts_DataSo urce"

DataTextField=" Account" DataValueField= "Account" AutoPostBack="T rue"
SelectedValue=' <%# Bind("Account") %>' OnSelectedIndex Changed="CheckF orDup"
Width="65px">

</asp:DropDownLis t>

<asp:DropDownLi st ID="DropDownLis t2" runat="server"
DataSourceID="D DL_Lname_DataSo urce"

DataTextField=" Lname" DataValueField= "Lname" Width="90px">

</asp:DropDownLis t>&nbsp;

<asp:ObjectData Source ID="DDL_Lname_D ataSource" runat="server"

InsertMethod="I nsert" OldValuesParame terFormatString ="original_{ 0}"
SelectMethod="G etLnameByAccoun t"

TypeName="Desk_ A_ServerTableAd apters.Customer TableAdapter">

<SelectParamete rs>

<asp:ControlPar ameter ControlID="Drop DownList1" Name="Account"
PropertyName="S electedValue"

Type="String" />

</SelectParameter s>

<InsertParamete rs>

<asp:Paramete r Name="Account" Type="String" />

<asp:Paramete r Name="broker" Type="String" />

<asp:Paramete r Name="key" Type="String" />

<asp:Paramete r Name="Fname" Type="String" />

<asp:Paramete r Name="Lname" Type="String" />

</InsertParameter s>

</asp:ObjectDataS ource>

<asp:ObjectData Source ID="DDL_Accts_D ataSource" runat="server"

InsertMethod="I nsert" OldValuesParame terFormatString ="original_{ 0}"
SelectMethod="G etCustomerByBro kerID"

TypeName="Desk_ A_ServerTableAd apters.Customer TableAdapter">

<SelectParamete rs>

<asp:SessionPar ameter Name="broker" SessionField="I B_Acct" Type="String" />

</SelectParameter s>

<InsertParamete rs>

<asp:Paramete r Name="Account" Type="String" />

<asp:Paramete r Name="broker" Type="String" />

<asp:Paramete r Name="key" Type="String" />

<asp:Paramete r Name="Fname" Type="String" />

<asp:Paramete r Name="Lname" Type="String" />

</InsertParameter s>

</asp:ObjectDataS ource>

</EditItemTemplat e>

<ItemTemplate >

<asp:Label ID="Label1" runat="server" Text='<%# Bind("Account")
%>'></asp:Label>

</ItemTemplate>

</asp:TemplateFie ld>

<asp:TemplateFi eld HeaderText="# of Contracts" SortExpression= "value">

<EditItemTempla te>

<asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("value") %>'
Width="50px"></asp:TextBox>

</EditItemTemplat e>

<ItemTemplate >

<asp:Label ID="Label2" runat="server" Text='<%# Bind("value")
%>'></asp:Label>

</ItemTemplate>

</asp:TemplateFie ld>

<asp:TemplateFi eld HeaderText="Typ e" SortExpression= "type">

<EditItemTempla te>

<asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("type") %>'
Width="50px"></asp:TextBox>

</EditItemTemplat e>

<ItemTemplate >

<asp:Label ID="Label3" runat="server" Text='<%# Bind("type")
%>'></asp:Label>

</ItemTemplate>

</asp:TemplateFie ld>

</Columns>

</asp:GridView>