MainWindow.xaml

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid" x:Class="CustomFilterPopupExample.MainWindow"
    xmlns:local="clr-namespace:CustomFilterPopupExample"
    xmlns:dxfui="http://schemas.devexpress.com/winfx/2008/xaml/core/filteringui"
    Title="MainWindow" Height="350" Width="525">
    <Window.DataContext>
        <local:TaskViewModel/>
    </Window.DataContext>
    <Grid>
        <dxg:GridControl ItemsSource="{Binding List}" AutoGenerateColumns="AddNew" x:Name="grid">
            <dxg:GridControl.View>
                <dxg:TableView x:Name="view">
                    <dxg:TableView.FilterEditorTemplate>
                        <DataTemplate>
                            <dxfui:FilterEditorControl QueryOperators="OnQueryOperators" />
                        </DataTemplate>
                    </dxg:TableView.FilterEditorTemplate>
                </dxg:TableView>
            </dxg:GridControl.View>
        </dxg:GridControl>
    </Grid>
</Window>