Loading ascx control Using C# code

im having some troubles in firing imagebutton click event in a user control which is loaded when the combo selectedIndexChanged event fires...
 
the user control is this
 

<divid="rowsBg"class="rowsBgSearchStaff"runat="server"><divid="trashHolder"class="buttonHolder"><asp:ImageButtonID="btnTrash"CssClass="btnTrashSearch"ToolTip="حذف"ImageUrl="~/img/btnsearchtrash.png"runat="server"onclick="btnTrash_Click"/></div><divid="separator1"class="separatorSearchStaff"></div><divid="editHolder"class="buttonHolder"><asp:ImageButtonID="btnEdit"CssClass="btnEditSearch"ToolTip="ویرایش"ImageUrl="~/img/btnsearchedit.png"runat="server"onclick="btnEdit_Click"/></div><divid="separator2"class="separatorSearchStaff"></div><divid="infoStaffHolder"class="staffinfoHolder"><asp:LabelID="lblStaffInfo"runat="server">Name, Family, Code</asp:Label></div></div>

 

and these are events:
 

protectedvoid btnTrash_Click(object sender, ImageClickEventArgs e)
    {
        dbm.Execute(String.Format("delete from Staff where Code='{0}'", StaffCode));
        dbm.Execute(String.Format("delete from Contract where StaffCode='{0}'", StaffCode));
        dbm.Execute(String.Format("delete from WardStaffs where StaffCode ='{0}'", StaffCode));
        rowsBg.Visible = false;
    }
    protectedvoid btnEdit_Click(object sender, ImageClickEventArgs e)
    {
        Response.Redirect(String.Format("EditStaff.aspx?sid={0}", StaffCode));
    }

 
TIP: dbm is an instance of my databasemanager class
 
in my aspx page I use below codes to add control manually
 

protectedvoid cmbBxWard_SelectedIndexChanged(object sender, RadComboBoxSelectedIndexChangedEventArgs e)
    {
        if (dbm.Read(String.Format("select * From Staff where Staff.Code in (select StaffCode from WardStaffs where WardCode={0})", cmbBxWard.Items[cmbBxWard.SelectedIndex].Value)))
        {
            foreach (DataRow dr in dbm.DT.Rows)
            {
                Control cnt = Page.LoadControl("StaffItem.ascx");
                StaffItem staff = (StaffItem)cnt;
                staff.StaffCode = dr["Code"].ToString();
                itemHolder.Controls.Add(staff);
            }
        }
    }

 
itemHolder is my div tag which hast runat="server" attribute
StaffItem is my control
after I change the selected item in my combobox I will click the btnEdit of my control
but it does not fire
 
why?
 
help me please