如何让用户在XAML中定义自定义属性？

<Window x:Class="MyApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:MyApp"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <local:CustomClass x:Key="CustomObject" MyProperty="CustomValue" />
    </Window.Resources>
    <Grid>
        <TextBlock Text="{Binding Source={StaticResource CustomObject}, Path=MyProperty}" />
    </Grid>
</Window>