[Parameter]
public RenderFragment Columns { get; set; }

<DxTreeList Data="TreeListData" KeyFieldName="ID" ParentKeyFieldName="RegionID">
    <Columns>
        <DxTreeListBandColumn Caption="Sales">
            <Columns>
                <DxTreeListDataColumn FieldName="Region" />
                <DxTreeListDataColumn FieldName="MarchSales" Caption="March" DisplayFormat="c0" />
                <DxTreeListDataColumn FieldName="SeptemberSales" Caption="September" DisplayFormat="c0" />
            </Columns>
        </DxTreeListBandColumn>
        <DxTreeListBandColumn Caption="Year-Over-Year Comparison">
            <Columns>
                <DxTreeListDataColumn FieldName="MarchChange" Caption="March" DisplayFormat="p2" />
                <DxTreeListDataColumn FieldName="SeptemberChange" Caption="September" DisplayFormat="p2" />
            </Columns>
        </DxTreeListBandColumn>
        <DxTreeListDataColumn FieldName="MarketShare" DisplayFormat="p0" />
    </Columns>
</DxTreeList>

@code {
    object TreeListData { get; set; }
    protected override void OnInitialized() {
        TreeListData = SalesByRegionDataProvider.GenerateData();
    }
}