DetailsView and DropdownList binding

[viktor]

Can some body help me. Look at at the code bellow
<InsertItemTemplate>

<asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("item_id") %>'
Visible="False"></asp:TextBox>

<aspropDownList ID="DropDownList1" runat="server"
DataSourceID="item_retreive"

DataTextField="item_id" DataValueField="inv_mast_uid" SelectedValue='<%#
Bind("inv_mast_uid") %>' AutoPostBack="True" >

</aspropDownList>

</InsertItemTemplate>

after the post back inv_mastUID field is still empty. what am i doing wrong?