In WebDataGrid column, I had used UnBoundField for displaying Dropdown. On Add button(which is placed outside grid) click, I want to display dropdown in unbounded field, otherwise this unbounded field will display already saved text(ie no dropdown in grid.)

Below is the code I am using to display dropdown

<ig:WebDataGrid ID="WebDataGrid1" runat="server" Height="400px"
        Width="100%" AutoGenerateColumns="false" DataKeyFields="ID" >
 <Columns>
 
  <ig:UnboundField Key="Name" Width="350px" Header Text="Name" /> </ig:UnboundField>
  .......
 <Columns>
 <EditorProviders>
            <ig:DropDownProvider ID="NameProvider">
                <EditorControl ID="editName" runat="server" DisplayMode="DropDownList" 
                    TextField="SName" ValueField="SName" />
            </ig:DropDownProvider>
</EditorProviders>

 <Behaviors>
            <ig:EditingCore>
                <Behaviors>
                    <ig:CellEditing Enabled="true">
                        <ColumnSettings>
                            <ig:EditingColumnSetting ColumnKey="Name" EditorID="NameProvider" />

  </ColumnSettings>
                    </ig:CellEditing>
                </Behaviors>
            </ig:EditingCore>
        </Behaviors> 
</ig:WebDataGrid>
<asp:Button Id="btnAdd" runat="server" Text="Add Name" onclick="btnAdd_Click"/>

What's the best way to show dropdown in some rows on unboundedField?