<TelerikGrid Data="@Data">
    <GridColumns>
        @*<GridColumn Title="Title">
        <Columns>*@
            <GridColumn Field="ID" />
        @*</Columns>
        </GridColumn>*@
        <GridColumn Title="Group">
            <Columns>
                <GridColumn Field="Name" />
            </Columns>
        </GridColumn>
    </GridColumns>
</TelerikGrid>

@code {

    public List<GridItem> Data { get; set; } = new List<GridItem>() {
        new GridItem() { ID = 1, Name = "Name 1" }
    };

    public class GridItem
    {
        public int ID { get; set; }
        public string Name { get; set; }
    }
}