Validating dropdownlist inside gridview control - asp.net

Question

for testing i have tried customvalidation
function ClientValidate(sender, args) {
//return false for testing...
args.IsValid = false;
}
<asp:CustomValidator runat="server" ID="CustomValidator1" ControlToValidate="ddldetail"
Text="Please select" ValidateEmptyText="true"
ClientValidationFunction="ClientValidate"
Display="Dynamic">
</asp:CustomValidator>
edit: here is what i exaclty wants to happen:
how to validate a dropdownlist and i have done this zillion times but what i am doing wrong here? any second pair of eye might spot it? i am trying to validate the dropdownlist if the user have not select any help?
<asp:Button ID="btn" runat="server" Text="Submit" OnClick="btn_Click" CausesValidation="true"/>
<asp:GridView ID="GVInputMapping" runat="server" AutoGenerateColumns="False" DataKeyNames="Id"
EnableModelValidation="True" onrowdatabound="GVInputMapping_RowDataBound">
<Columns>
<asp:BoundField DataField="Name" ControlStyle-Width="250px" HeaderText="Name" SortExpression="Name" />
<asp:TemplateField>
<ItemTemplate>
<asp:DropDownList runat="server" ID="ddldetail">
<asp:ListItem Selected="True" Value="0">Select me</asp:ListItem>
<asp:ListItem Value="1">abc</asp:ListItem>
<asp:ListItem Value="2">GHt</asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator ID="requiredDDL" runat="server"
ControlToValidate="ddldetail" ErrorMessage="Please select" InitialValue="Select me" Display="Dynamic"></asp:RequiredFieldValidator>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>

Answer 1

You have the InitialValue of the validator set to Select me, but the Value of that item is actually 0:
<asp:DropDownList ID="DropDownList1" runat="server">
<asp:ListItem Text="Select Me" Value="0" />
<asp:ListItem Text="Foo" Value="1" />
<asp:ListItem Text="Bar" Value="2" />
</asp:DropDownList>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
ControlToValidate="DropDownList1"
ErrorMessage="Please select"
InitialValue="0"
Display="Dynamic">
</asp:RequiredFieldValidator>
You'll also need to assign a unique validation group for each row, otherwise validation will kick off for every row. To assign a unique validation group, you can use the Id column:
ValidationGroup='<%# string.Format("Group_{0}", Eval("Id")) %>'
You would add this to the validator and the button in the row.