Here's the source code of the detailsview and objectdatasource:
 
<asp:ObjectDataSource ID="CustomerDetailDataSource" runat="server"
DataObjectTypeName="Customer"  DeleteMethod="Delete"
SelectMethod="GetCustomerByID" TypeName="CustomerManager"
UpdateMethod="UpdateCustomer">
     <SelectParameters>
          <asp:Parameter DefaultValue="0" Name="ID" Type="Int32" />
     </SelectParameters>
</asp:ObjectDataSource>
 
<asp:DetailsView ID="DetailsView1" runat="server"
AutoGenerateRows="False" DataSourceID="CustomerDetailDataSource"
DefaultMode="Edit">
      <Fields>
            <asp:BoundField DataField="fname" HeaderText="fname"
SortExpression="fname" />
            <asp:BoundField DataField="lname" HeaderText="lname"
SortExpression="lname" />
            <asp:BoundField DataField="email" HeaderText="email"
SortExpression="email" />
            <asp:BoundField DataField="ID" HeaderText="ID"
SortExpression="ID" ReadOnly="true"/>
            <!--
            WITHOUT THE NEXT LINE, VERSION IS NULL WHEN UPDATING THE
ENTITY, WITH THE NEXT LINE I GET AN EXCEPTION WHEN UPDATING
             -->
            <asp:BoundField DataField="version" HeaderText="version"
SortExpression="version"  ReadOnly="true"/>
      </Fields>
</asp:DetailsView>
 
This is what I call in my updatebutton's event handler:
 
DetailsView1.UpdateItem(true);