Full postback triggered by LinkButton inside GridView inside UpdatePanel

<asp:ScriptManager ID="ContentScriptManager" runat="server"/>
<asp:UpdatePanel ID="ContentUpdatePanel" runat="server"ChildrenAsTriggers="true">
    <ContentTemplate>
        <asp:GridView ID="OrderGrid" runat="server"AllowPaging="false"AllowSorting="false"
            AutoGenerateColumns="false">
            <Columns>
                <asp:TemplateFieldHeaderText="">
                    <ItemTemplate>
                        <asp:LinkButton ID="MarkAsCompleteButton" runat="server"Text="MarkAsComplete"
                            CommandName="MarkAsComplete"CommandArgument=‘<%# Eval("Id") %>‘/>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:BoundFieldDataField="Name"HeaderText="Name"/>
                <asp:BoundFieldDataField="LoadDate"HeaderText="Load Date"/>
                <asp:BoundFieldDataField="EmployeeCutOffDate"HeaderText="Cut Off Date"/>
                <asp:BoundFieldDataField="IsComplete"HeaderText="Is Completed"/>
            </Columns>
        </asp:GridView>
    </ContentTemplate>
</asp:UpdatePanel>

protected void OrderGrid_RowDataBound(object sender, GridViewRowEventArgs e)  
{  
   LinkButton lb = e.Row.FindControl("MarkAsCompleteButton") as LinkButton;  
   ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(lb);  
}