session check for disable & enable checkbox C#

I'm beginner & I need help I try this code for check the id for employee to enable or disable the checkbox depend on the id for employee but the checkbox was disabled even when I login with the same Id in the session

    if (Session["employeeNo"] == "12345") 
    {
        CheckBoxList1.Enabled = true;
    }

    else
    {
        CheckBoxList1.Enabled = false;
    }