You have a DetailsView control with edit / add and all the other goodness enabled, but when adding a new record you want a non-visible field to get it’s value from another control like the SelectedValue of a GridView or a DropDownList in the InsertParameters collection of your SqlDataSource just use a ControlParameter instead

[codesyntax lang=”csharp”]

    <asp:ControlParameter ControlID="ddlYourList" Name="ParameterName"
        PropertyName="SelectedValue" Type="Int32" />
    <asp:Parameter Name="SomeDetailsViewParameter" Type="String" />