retrieve CheckBoxList multiple values in code behind

Hi all,
I am using a CheckBoxList in order for the user to select multiple items:
<td>
Shift Preference:(Multiple Selections Permitted)<br />
<asp:CheckBoxList ID="shiftPreferenceList" SelectionMode="Multiple" runat="server">
<asp:ListItem Value="">None</asp:ListItem>
<asp:ListItem Value="1st Shift">1st Shift</asp:ListItem>
<asp:ListItem Value="2nd Shift">2nd Shift</asp:ListItem>
<asp:ListItem Value="3rd Shift">3rd Shift</asp:ListItem>
<asp:ListItem Value="Weekends">Weekends</asp:ListItem>
<asp:ListItem Value="Overtime">Overtime</asp:ListItem>
<asp:ListItem Value="Holidays">Holidays</asp:ListItem>
</asp:CheckBoxList>
</td>
I need to read the value(s) chosen ...