MainWindow.xaml

<dx:ThemedWindow
    x:Class="DataTable.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
    xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid"
    xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
    xmlns:local="clr-namespace:DataTable"
    Width="1000"
    Height="800"
    Title="MainWindow">
    <dx:ThemedWindow.DataContext>
        <local:MainViewModel />
    </dx:ThemedWindow.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <dxg:GridControl
            AutoGenerateColumns="AddNew"
            ItemsSource="{Binding Items}"
            Name="Grid">
            <dxg:GridControl.View>
                <dxg:TableView Name="view" />
            </dxg:GridControl.View>
        </dxg:GridControl>
        <StackPanel Grid.Row="1">
            <Button Content="Add a new column">
                <dxmvvm:Interaction.Behaviors>
                    <dxmvvm:CompositeCommandBehavior>
                        <dxmvvm:CommandItem Command="{Binding AddColumnCommand}" />
                        <dxmvvm:CommandItem Command="{DXCommand '@e(Grid).PopulateColumns()'}" />
                    </dxmvvm:CompositeCommandBehavior>
                </dxmvvm:Interaction.Behaviors>
            </Button>
        </StackPanel>
    </Grid>
</dx:ThemedWindow>