Whether an element is a markup extension is decided by walking its base
types, and that walk leaves the assemblies the document's own assembly
references: WPFLocalizeExtension's LocExtension, in the report, derives
from a type in XAMLMarkupExtensions, which the application never
references itself. Only the assemblies named by the module were loaded,
so the base type resolved to nothing, the extension was not recognised,
and it went out as an element tree carrying the decompiler's own
placeholder namespace - https://github.com/icsharpcode/ILSpy - into the
XAML.
The reference closure is now followed transitively. It is built once per
assembly, and the cost is bounded: for a .NET 8 WPF application the type
system grows from 87 to 158 modules and from 92 to 118 ms, for a .NET
Framework one from 9 to 24 modules and 39 to 44 ms. Over the 1158 BAML
documents of a DevExpress theme assembly the output does not change at
all - this only decides cases that used to resolve to nothing.
Assisted-by: Claude:claude-opus-5:Claude Code
Siegfried Pammer
03588ba4ae