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Cannot retrieve a correct instance from a ListBox in a User Contro

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I'm trying to develop a simple Web User Control that contains two list
boxes, Add and Remove buttons. This User Control transfers the selected
items from left list box to right list box and vice-versa, depending on the
button clicked. The SelectionMode of both list boxes is "Multiple" and
AutoPostBack is set to false.

Here is the simple process:
string strItemsToKeep = "";
// Collect all items selected from lbLeftList list box.
foreach( ListItem item in lbLeftList.Items )
if( item.Selected )
lbRightList.Items.Add( item.Text );
strItemsToKeep = strItemsToKeep + item.Text + ";";
Then after the loop, I process the string and load it back to the left list
box. This works great within a simple aspx page.

But, here's my problem:
In a User Control ascx page, in the Code Behind, for each item retrieved
from lbLeftList, I can see the data in each item.Text but the item.Selected
is always false.

After searching on the Web, I tried the following:
System.Web.UI.UserControl UserControl;
UserControl =
(System.Web.UI.UserControl)Parent.FindControl("Dou ble_list_control1");
//which is the name of the User Control in the parent page.

System.Web.UI.WebControls.ListBox lb;
lb = (System.Web.UI.WebControls.ListBox)UserControl.Fin dControl("lbLeftList");

I thought that I could finally retrieve the correct information but, once
again, I have the same problem: the lb.Items[0].Selected (which is the one I
selected) is also set to false.

I really do not understand what is going on. If somebody can help me it
will greatly be appreciated.

Thank you very much.
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