Validation of a detailsview field against a numeric value

Validation of a field inside a detailsview does not need to be done with the Updating or Editing events, but can be accomplished by a simple validation control in the markup language. Convert the field in the detailsview to a template field, and use a standard validation control.

<asp:CompareValidator ID="CompareValidator2" runat="server"
    ErrorMessage="Numeric input required"
    Operator="DataTypeCheck"
    Type="Double"
    ControlToValidate="TextBox2">
</asp:CompareValidator>

And applied to a data bound field:

<asp:TemplateField HeaderText="Cost amount" SortExpression="wsCostAmount">
<EditItemTemplate>
    <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("wsCostAmount") %>'></asp:TextBox>
    <asp:CompareValidator ID="CompareValidator1" runat="server"
        ErrorMessage="Numeric input required"
        Operator="DataTypeCheck"
        Type="Double"
        ControlToValidate="TextBox2"></asp:CompareValidator>
</EditItemTemplate>
<InsertItemTemplate>
    <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("wsCostAmount") %>'></asp:TextBox>
    <asp:CompareValidator ID="CompareValidator2" runat="server"
        ErrorMessage="Numeric input required"
        Operator="DataTypeCheck"
        Type="Double"
        ControlToValidate="TextBox2">
    </asp:CompareValidator>
</InsertItemTemplate>
<ItemTemplate>
    <asp:Label ID="Label2" runat="server" Text='<%# Bind("wsCostAmount") %>'></asp:Label>
</ItemTemplate>