'DropDownList1' has a SelectedValue which is invalid is killing me

I have 2 datasources
datasourceA is add new record to a database which does not have record now.
another datasourceB is get a list and become datasource of a dropdownlist within a Formview that insert record to datasourceA
I use
<asp:DropDownList ID="DropDownList1" runat="server" DataSourceID="SqlDataSourceA"  AutoPostBack="true"                             DataTextField="Name" DataValueField="ID"                             SelectedValue='<%# Eval("ID") %>'>                       ...