Using DropDownList in FromView control - asp.net

Question

I'm trying to get a drop down list control to work in FormView. I need to have the list be a filtered view of a certain table and still be bound to a field in the data I'm editing. I've tried setting the item data programatically, ant that works but then the data binding
doesn't work, It tries to insert null into the database.
This is the code I've tried. I've also tried doing the same thing in several other events, it still tries to insert null into the database.
<asp:DropDownList ID="lstManagers" runat="server"
OnDataBound ="ManagersLoad"
SelectedValue='<%# Bind("UserName") %>' Width="100%"
DataSourceID="TimeOff" DataTextField="UserName" DataValueField="UserName">
</asp:DropDownList>
Protected Sub ManagersLoad(ByVal sender As Object, ByVal e As System.EventArgs)
Dim lst As DropDownList = FormView1.FindControl("lstManagers")
'get list of managers
Using ef As New TimeOffData.TimeOffEntities
For Each item As ListItem In lst.Items
Dim li As ListItem = item
item.Text = (From x In ef.TimeOffUsers Where x.UserName = li.Value Select x.FirstName & " " & x.LastName).FirstOrDefault
Next
End Using
End Sub

Answer 1

I took all the data binding stuff of the control and just decide it would be easier to do it manually. I've changed the code to this,
Protected Sub FormView1_ItemInserting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.FormViewInsertEventArgs) Handles FormView1.ItemInserting
Dim lst As DropDownList = FormView1.FindControl("lstManagers")
e.Values.Item("ManagerName") = lst.SelectedValue
End Sub
Protected Sub ManagersLoad(ByVal sender As Object, ByVal e As System.EventArgs)
Dim lst As DropDownList = FormView1.FindControl("lstManagers")
'get list of managers
Using ef As New TimeOffData.TimeOffEntities
Dim mng = From x In ef.TimeOffUsers Where x.IsManager = True
For Each item In mng
lst.Items.Add(New ListItem(item.FirstName & " " & item.LastName, item.UserName))
Next
End Using
End Sub