There are few ways to do this.
One is by modifying the
ItemTemplate
in
TemplateField
<asp:templatefield headertext="Description" xmlns:asp="#unknown">
<itemtemplate>
<asp:label id="lblDescription" runat="server">
Text='<%# Limit(Eval("Description"),10) %>'
Tooltip='<%# Eval("Description") %>'>
</asp:label>
</itemtemplate>
</asp:templatefield>