Question

I have a WPF project with an AssemblyInfo.cs that groups multiple CLR namespaces into a single XML namespace:

[assembly: XmlnsDefinition("http://foo.bar", "MyLibary.Controls")]
[assembly: XmlnsDefinition("http://foo.bar", "MyLibary.Converters")]

In XAML this is used like so:

<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:fb="http://foo.bar">
    <fb:FooButton IsEnabled="{Binding Something, Converter={fb:FooConverter}}"/>
</UserControl>

This works great when the XAML is instantiated normally, but now I am now trying to dynamically load XAML files from my project using XamlReader.

The problem: I can’t seem to map multiple CLR namespaces to a single XML namespace. It seems that the last definition added to the XamlTypeMapper is the only one that persists (e.g. it clobbers previous registrations):

var parserContext = new ParserContext();
parserContext.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
parserContext.XmlnsDictionary.Add("fb", "http://foo.bar");

parserContext.XamlTypeMapper = new XamlTypeMapper(new string[] {"MyLibrary"});
parserContext.XamlTypeMapper.AddMappingProcessingInstruction("http://foo.bar", "MyLibrary.Converters", "MyLibrary");
parserContext.XamlTypeMapper.AddMappingProcessingInstruction("http://foo.bar", "MyLibrary.Controls", "MyLibrary");

...

var rootNode = XamlReader.Load(memeoryStream, parserContext) as FrameworkElement

The error message is:

'Cannot create unknown type '{http://foo.bar}MyConverter'.'

If all put all my code under a single common CLR namespace, everything works but unfortunately this is not option. Has anybody mapped multiple CLR namespaces to a single XML namespace for the purpose of loading XAML content dynamically?

Thanks in advance!

Answer 1

As mentioned in the comments above, the solution is to manually load the assembly before invoking XamlReader.Load and removing the type mapper and context all together:

Assembly.Load("MyLibrary");
var rootNode = XamlReader.Load(memeoryStream) as FrameworkElement

I would have assumed since the XamlTypeMapper is initialized with a list of assemblies, that this class would be responsible for loading the assembly (and maybe it is) but the behaviour of AddMappingProccessingInstruction prevents this from working.