Add AssemblyName support into XmlnsDefinition attribute

[wieslawsoltes]

Is your feature request related to a problem? Please describe.

I want to include types into https://github.com/avaloniaui namespace and to do that I want to use XmlnsDefinition but it does not support AssemblyName (you can add AssemblyName when using xmlns inside xaml file e.g. xmlns:sys="clr-namespace:System;assembly=mscorlib")

Describe the solution you'd like

Instead defining each time xmlns in xaml files like xmlns:sys="clr-namespace:System;assembly=mscorlib" I want to include them in Avalonia namespace via XmlnsDefinition

[assembly: XmlnsDefinition("https://github.com/avaloniaui ", "System", AssemblyName = "mscorlib")]

Describe alternatives you've considered

No response

Additional context

Instead:

xmlns:sys="clr-namespace:System;assembly=mscorlib"

<sys:Tuple x:TypeArguments="sys:Int32, sys:String"
           xmlns:sys="clr-namespace:System;assembly=mscorlib"
           xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <x:Arguments>
        <sys:Int32>42</sys:Int32>
        <sys:String>Hello World</sys:String>
    </x:Arguments>
</sys:Tuple>

we could have clean xaml syntax:

    <Tuple x:Key="Tuple" x:TypeArguments="Int32, String">
      <x:Arguments>
        <Int32>42</Int32>
        <String>Hello World</String>
      </x:Arguments>
    </Tuple>

[maxkatz6]

In Avalonia you can write xmlns:sys="using:System" without specifying any assembly, which I use often for this namespace. Doesn't the same work for [assembly: XmlnsDefinition("https://github.com/avaloniaui ", "System")] ?

[wieslawsoltes]

In Avalonia you can write xmlns:sys="using:System" without specifying any assembly, which I use often for this namespace. Doesn't the same work for [assembly: XmlnsDefinition("https://github.com/avaloniaui ", "System")] ?

[assembly: XmlnsDefinition("https://github.com/avaloniaui ", "System")] does not work

[wieslawsoltes]

Here is my test project https://github.com/wieslawsoltes/TupleDemo