How to put a dropdownlist in a gridview and update the database on user clicking update

<asp:GridView ID="gv_users" runat="server" DataSourceID="UserData" DataKeyNames="userId" OnDataBound="gv_users_DataBound" OnRowDataBound="gv_users_RowDataBound" CellPadding="4" ForeColor="#333333" GridLines="None" AllowPaging="True" AllowSorting="True" AutoGenerateColumns="False" BorderColor="Silver" BorderStyle="Solid" BorderWidth="1px" PageSize="5" Width="600px" 
             AutoGenerateDeleteButton="True" AutoGenerateEditButton="True">
            <Columns>
                <asp:BoundField DataField="userID" HeaderText="userId" ReadOnly="True" SortExpression="userId" Visible="False" />
 
                <asp:TemplateField HeaderText="User Type">
                    <EditItemTemplate>
                        <asp:Label Text="<%# Bind("description") %>" runat="server"/>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:DropDownList DataSource='<%# GetUserTypes() %>' DataTextField="description" DataValueField="type" ID="ddlUserType" runat="server">
                        </asp:DropDownList>
                    </ItemTemplate>
                    
                </asp:TemplateField>
                          
                <asp:BoundField DataField="firstName" HeaderText="First Name" SortExpression="firstName" />
                <asp:BoundField DataField="lastName" HeaderText="Last Name" SortExpression="lastName" />
                <asp:BoundField DataField="email" HeaderText="Email" SortExpression="email" HeaderStyle-Width="200" />
            </Columns>
            
            <pagerstyle backcolor="#999999" forecolor="Black" horizontalalign="Center" />   
            <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
            <RowStyle BackColor="#E3EAEB" />
            <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />
            <HeaderStyle BackColor="Gray" Font-Bold="True" ForeColor="White" HorizontalAlign="Left" />
            <EditRowStyle BackColor="#7C6F57" />
            <AlternatingRowStyle BackColor="White" />
        </asp:GridView>
        <asp:SqlDataSource ID="UserData" runat="server" ConnectionString="<%$ ConnectionStrings:DBTConnectionString %>" 
            SelectCommand="SELECT * FROM PFC_users u join PFC_xref_userType ut on u.userType = ut.type" 
            InsertCommand="INSERT INTO PFC_users(firstName, lastName, country) VALUES(@firstName, @lastName, @country)"
            DeleteCommand="DELETE FROM PFC_users WHERE userID = @userID " 
            UpdateCommand="UPDATE PFC_users SET firstName = @firstName, lastName = @lastName, country = @country WHERE userID = @userID">             
        </asp:SqlDataSource>