You can disable AutoGenerateColumn per your dataset assigned and add TextBox control as below.
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="text1" runat="server" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>