Forms Data Controls :: Gridview Doesn't Sort On A Specific Column After Updating

I have been struggling with this problem for a long time. Does anyone have any clue about this problem? I created a gridview and set the allowsorting to true. This gridview has four columns: Name, Position, StartDate, and EndDate. I want the gridview to be sorted on the EndDate.

Inside of the save event, I called the BindGrid() function to rebind the datasource to the gridview. The changes will shown immediately, but the problem is that the records are not sorting on EndDate. I have to refresh the page manually to get the view sorted.

<asp:GridView ID="gvInfos" runat="server"
CheckBoxEnabled = "true"
ShowEmptyTable = "true"
AutoGenerateColumns = "False"
CssClass = "gv_white"
DataKeyNames = "Id"
GridLines = "None"
Width = "100%"
AllowSorting = "true"
>
<Columns>
<asp:ButtonField CommandName="Select" DataTextField="Name" HeaderText="Name" />
<asp:BoundField DataField="Position" HeaderText="Position" />
<asp:BoundField DataField="StartDate" HeaderText="Start Date"
DataFormatString="{0:Y}" />
<asp:TemplateField HeaderText="End Date" SortExpression="EndDate">
<ItemTemplate>
<%# (((DateTime)Eval("EndDate")).Year == (DateTime.MaxValue.Year) || (DateTime)Eval("EndDate") == null) ? "Present" : ((DateTime)Eval("EndDate")).ToString("y")%>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>