It still doesn't work correctly.  Here's my code:

 <form id="form1" runat="server">
    <div>
      <asp:ScriptManager ID="ScriptManager1" runat="server">
      </asp:ScriptManager>
      <ig:WebDropDown ID="WebDropDown1" runat="server" Width="200px"  TextField="Prod_Code" ValueField="Prod_ID"
        AutoSelectOnMatch="false"  EnableAutoFiltering="Client"
        OnSelectionChanged="WebDropDown1_SelectionChanged"
        DataSourceID="SqlDataSource1">
        <AutoPostBackFlags SelectionChanged="On" ValueChanged="Off" />
      </ig:WebDropDown>
   
      <asp:SqlDataSource ID="SqlDataSource1" runat="server"
        ConnectionString="<%$ ConnectionStrings:TravelerMakerGUIConnectionStringXXXX %>"
        SelectCommand="SELECT [Prod_Code], [Prod_ID] FROM [ProductCodes]">
      </asp:SqlDataSource>
   
    </div>
    </form>


The desired behavior is: A postback should only happen when:
1) an item is selected with the mouse (this works)
2) Only when the <enter> key is hit (not working) - postpacks also happen at other times.

If the list is a bunch of part numbers like:
abc-123
abc-124
abc-125
def-123
def-124

Now, using my code and part numbers from above, select abc-124 with the mouse.  a postback happens - this is correct.

Now, pretend that you made a mistake, and you really wanted one of the def-123 parts.  So, rather than use the mouse, you highlight the abc-123 item, and start typing 'D'.....     A postback happens.   I did not select a full partnumber, I just typed a 'D', and a postback happened.  This postback should not happen, I did not select a part number.   

A postback should only happen if an item is selected with the mouse, or if I hit the <enter> key. 

Thanks, Jim