Feature layer definition expression

<UserControl
    x:Class="ArcGISRuntime.UWP.Samples.FeatureLayerDefinitionExpression.FeatureLayerDefinitionExpression"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:esriUI="using:Esri.ArcGISRuntime.UI.Controls">
    <Grid>
        <esriUI:MapView x:Name="MyMapView" />
        <Border Style="{StaticResource BorderStyle}">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Button Content="Apply expression"
                        Grid.Column="0"
                        HorizontalAlignment="Stretch"
                        Margin="0,0,2.5,0"
                        Click="OnApplyExpressionClicked" />
                <Button Content="Reset expression"
                        Grid.Column="1"
                        HorizontalAlignment="Stretch"
                        Margin="2.5,0,0,0"
                        Click="OnResetButtonClicked" />
            </Grid>
        </Border>
    </Grid>
</UserControl>