A minimal example demonstrating how to use Markup Extensions to handle compile-time conditional XAML content in WPF applications.

This project demonstrates how to:

• Create a custom Markup Extension for conditional XAML content
• Use preprocessor directives to control content at compile time
• Avoid XAML duplication and visibility bindings

<Button Content="{local:FeatureCondition
    WhenEnabled='New Content',
    WhenDisabled='Original Content'}" />

Build original version:

msbuild.exe MarkupExtensionDemo.csproj

Build with new feature enabled:

msbuild.exe MarkupExtensionDemo.csproj /p:DefineConstants="fix_issue_001"

• Visual Studio 2019
• .NET Framework
• WPF

• Clean the solution between builds when switching preprocessor directives
• The example shows both simple text switching and a counter increment (by 1 or 2)
• Uses MarkupExtension for cleaner, more maintainable conditional XAML