Difference between Xaml Readers of System.Xaml and System.Windows.Markup?

Question

There are two Xaml Readers. One of them is included in System.Xaml the other one is included in System.Windows.Markup. What is the difference between them?

Answer 1

Taken from MSDN:

WPF types and the WPF technology in general support concepts that rely on access to WPF internals. For instance, how WPF implements dependency properties relies on internal techniques for efficient type-member lookup. Access to these internals is enabled by the XAML reading and writing APIs provided in XamlWriter and XamlReader from the System.Windows.Markup namespace and PresentationFramework assembly. However, the lower-level XAML readers and XAML writers from the System.Xaml assembly (classes based on System.Xaml.XamlReader, System.Xaml.XamlWriter) do not have access to the WPF internals. There is no dependency from System.Xaml to any WPF-specific assembly. Without access to the WPF internals, System.Xaml readers and writers cannot correctly load or save all WPF types, or types based on WPF types. In particular, the System.Xaml readers and writers do not understand concepts such as the WPF dependency property backing property store, or all the specifics of how WPF uses styles, resource dictionaries and templates. Therefore you have a choice to make:

• If you are loading WPF types, and/or you are using XAML in BAML form in any way, use the PresentationFramework XAML readers and XAML writers.
• If you are not relying on any WPF types or the BAML form of XAML, and are not using another specific technology's XAML reader or XAML writer implementation for reasons that are specific to that framework, use the System.Xaml XAML readers and XAML writers.