Customising the asp.net grid view sorting behaviour

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ASP.NET

I have a asp.net grid view in my page

<asp:GridView runat="server" ID="_jobsGridView" GridLines="None" style="width: 100%;" OnRowDataBound="GridView_RowDataBound" AllowSorting="true" OnSorting="gridView_sorting">
<HeaderStyle CssClass="joblistview_header_row" />
<rowstyle cssclass="joblistview_row" />
<alternatingrowstyle cssclass="joblistview_row joblistview_row_alternative" />
<SelectedRowStyle CssClass="joblistview_row joblistview_row_highlight" />

i have kept the AllowinSorting to true and associated OnSorting to a "gridView_sorting" method.

I want to customise the sorting of the column. If my input values are
7,8,9,1,2,10,11 then my sorted list will look like 1,10,11,2,3,4,5,6,7,8,9
i want my output to be 1,2,3,4,5,6,7,8,9,10,11.

I am using DataTable object as data source to GridView