3rdpartylibs/fastreports.wpf/Demos/WPF/UserFunctions/MainWindow.xaml

<Window x:Class="UserFunctions.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        Title="Custom Functions" Height="253" Width="270" ResizeMode="NoResize">
    <Grid>
        <Button Content="Run the designer" HorizontalAlignment="Left" Width="150" Margin="58,56,0,0" VerticalAlignment="Top" Click="Button_Click"/>
        <TextBlock HorizontalAlignment="Left" Margin="52,94,0,0" TextWrapping="Wrap" Text="Custom functions can be seen in the Data window under the &quot;Functions&quot; node." VerticalAlignment="Top" Height="57" Width="162"/>

    </Grid>
</Window>