Use 'SortExpression' to those columns only which you want to sort .
See for example in which column 'Melder' doesnot have SortExpression so you can't sort this column but other can sort :
<asp:GridView ID="gvOutlookMeldingen" runat="server"
AllowSorting="True"
OnSorting="gvOutlookMeldingen_Sorting"
AutoGenerateColumns="False"
AutoGenerateSelectButton="True"
onselectedindexchanged="GridView_SelectedIndexChanged">
<Columns>
<asp:BoundField DataField="Melder" HeaderText="Melder" />
<asp:BoundField DataField="Onderwerp" HeaderText="Onderwerp" SortExpression="Onderwerp" />
<asp:TemplateField HeaderText="Omschrijving" SortExpression="Omschrijving">
<ItemTemplate>
<div style="overflow:auto; width: 500px; height: 200px;">
<asp:Label ID="lblOmschrijving" runat="server" Text='<%# Bind("Omschrijving")%>'></asp:Label>
</div>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Meldingsdatum" HeaderText="Meldingsdatum" SortExpression="Meldingsdatum" />
<asp:BoundField DataField="OutlookID" HeaderText="OutlookID" SortExpression="OutlookID" />
</Columns>
</asp:GridView>
on code behind:
protected void gvOutlookMeldingen_Sorting(object sender, GridViewSortEventArgs e)
{
switch (e.SortExpression)
{
case "Melder":
if (e.SortDirection == SortDirection.Ascending)
{
gvOutlookMeldingen.DataSource =
gvOutlookMeldingen.DataBind();
}
else
{
gvOutlookMeldingen.DataSource =
gvOutlookMeldingen.DataBind();
}
break;
}
}