Sorting with EntityGridView and DataSource

I am trying to sort using an EntityGridView, but it is not working.  Click on column headers refreshes the page, but sorting does not occur.  Can anybody help?  Here is my markup:

 <data:EntityGridView
                                AllowExportToExcel="false"
                                ID="gvAppointments"
                                DataKeyNames="ID"
                                runat="server"
                                AutoGenerateColumns="false"
                                DataSourceID="dsAppointments"
                                DefaultSortColumnName="StartTime"
                                DefaultSortDirection="Descending"
                                OnSorting="gvAppointments_Sorting"
                                OnSelectedIndexChanged="gvAppointments_SelectedIndexChanged"
                                AllowSorting="true"
                                AllowPaging="true"
                                CssClass="DataGrid"
                                HeaderStyle-ForeColor="White"
                                HeaderStyle-BackColor="#333366"
                                RowStyle-BackColor="#fbf4fb"
                                CellPadding="3"
                                CellSpacing="0"
                                AlternatingRowStyle-BackColor="White"
                                RowStyle-Font-Size="x-small"
                                AlternatingRowStyle-Font-Size="x-small"
                                HeaderStyle-Font-Size="x-small">
                                    <Columns>
                                        <asp:CommandField ShowSelectButton="true"/>
                                        <asp:BoundField DataField="StartTime" HeaderText="Start Time" SortExpression="StartTime" />
                                        <asp:BoundField DataField="EndTime" HeaderText="End Time" SortExpression="EndTime" />
                                        <asp:BoundField DataField="AppointmentType" HeaderText="Type" SortExpression="AppointmentType" />
                                        <asp:BoundField DataField="Cancelled" HeaderText="Cancelled" SortExpression="Cancelled" />
                                        <asp:BoundField DataField="CareProvider" HeaderText="Provider" SortExpression="CareProvider" />
                                        <asp:BoundField DataField="Facility" HeaderText="Facility" SortExpression="Facility" />
                                        <asp:BoundField DataField="Recommendation" HeaderText="Recommendation" SortExpression="Recommendation" />
                                        <asp:TemplateField HeaderText="">
                                         <ItemTemplate>
                                           <asp:Button ID="btnAptEdit"
                                             OnClientClick="<%# Eval(&quot;ID&quot;, &quot;return EditAppointment('{0}', 'edit');&quot;) %>"
                                             runat="server"
                                             text="Edit...">
                                             </asp:Button>
                                         </ItemTemplate>
                                        </asp:TemplateField>
                                    </Columns>
                                </data:EntityGridView>

 <data:PatientAppointmentDataSource EnableDeepLoad="true" ID="dsAppointments" EnableSorting="true" SelectMethod="GetByPatientID" runat="server">
        <DeepLoadProperties Method="IncludeChildren">
            <Types>
                <data:PatientAppointmentProperty Name="Reason" />
                <data:PatientAppointmentProperty Name="Facility" />
                <data:PatientAppointmentProperty Name="CareProvider" />
                <data:PatientAppointmentProperty Name="Reason" />
            </Types>
        </DeepLoadProperties>
        <Parameters>
            <asp:QueryStringParameter Type="Int32" Name="PatientID" QueryStringField="PatientID" />
        </Parameters>
    </data:PatientAppointmentDataSource>
   

rithomas,

 You could do this:

    protected void Page_Load(object sender, EventArgs e)
    {
        gvAppointments.Sorting += new GridViewSortEventHandler(gvAppointments_Sorting);
    }

    void gvAppointments_Sorting(object sender, GridViewSortEventArgs e)
    {
        gvAppointments.DefaultSortColumnName = e.SortExpression;
        gvAppointments.DefaultSortDirection = e.SortDirection;
    }

or using Find method with parameterized filter:

 <data:PatientAppointmentDataSource EnableDeepLoad="true" ID="dsAppointments" EnableSorting="true" SelectMethod="GetByPatientID" runat="server">
        <DeepLoadProperties Method="IncludeChildren">
            <Types>
                <data:PatientAppointmentProperty Name="Reason" />
                <data:PatientAppointmentProperty Name="Facility" />
                <data:PatientAppointmentProperty Name="CareProvider" />
                <data:PatientAppointmentProperty Name="Reason" />
            </Types>
        </DeepLoadProperties>
        <Parameters>
                 <data:SqlParameter Name="Parameters">
                    <Filters>
                        <data:PatientAppointmentFilter  Column="PatientID" ControlID="__Page" PropertyName="PatientID" />
                    </Filters>
                </data:SqlParameter>
                <data:CustomParameter Name="OrderByClause" Value="" ConvertEmptyStringToNull="false" />
        </Parameters>
    </data:PatientAppointmentDataSource>

code-behind: 

    public String PatientID
    {
        get
        {
            String q = Request.QueryString["PatientID"];
            if (q != null)
            {
                return q.ToString();
            }
            return string.Empty;
        }
    }