WPF XAML merge default namespace definitions

Question

In a WPF application, you can create XmlnsDefinitions to map multiple namespaces from another assembly into one reference .

You can take advantage of that to map your own namespaces to the Microsoft default XmlnsDefinition, for example:

[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "MyLibrary.MyControls")]

This way, you don't even need to add a reference to your namespace in the XAML file, because they are already mapped to the default "xmlns".

So, if I had a control called "MyControl", I can use it like this (without any namespaces or prefixes):

<MyControl />

My question is: Can I merge the default Microsoft namespaces into a single one?

For example: I want to get rid of the "xmlns:x" namespace by merging it into "xmlns". I would have to reference all the namespaces in "http://schemas.microsoft.com/winfx/2006/xaml" to "http://schemas.microsoft.com/winfx/2006/xaml/presentation".

Like this:

[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System...")]
[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System...")]
...

So I can turn this:

<Window x:Class="MyProject.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    >

Into this:

<Window Class="MyProject.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    >

Duplicate : stackoverflow.com/questions/47427705/…. string innerxml = "xsi:noNamespaceSchemaLocation=\"amzn-envelope.xsd\" xmlns:xsi=\"w3.org/2001/XMLSchema-instance\""; using (var writer = XmlWriter.Create(stream, settings)) { writer.WriteStartElement("AmazonEnvelope"); writer.WriteRaw(innerxml); writer.WriteEndElement(); } — jdweng
I put my UserControl into System.Windows.Controls. And it does not work for me: [assembly: System.Windows.Markup.XmlnsDefinition( "http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Controls" )] Looks like designer is seeing my class, but compiler not. Error: The tag 'ContentViewer' does not exist in XML namespace 'http://schemas.microsoft.com/winfx/2006/xaml/presentation' — Denis535

Athari Athari · Accepted Answer · 2017-11-22T21:55:27

You can't override existing namespace mappings as they are already present in the standard assembies, but you can try merging all .NET namespaces into your own XML namespace. Like this:

[assembly: XmlnsDefinition("urn:foobar", "System.Windows.Controls")]
[assembly: XmlnsDefinition("urn:foobar", "System.Windows.Documents")]
[assembly: XmlnsDefinition("urn:foobar", "System.Windows.Shapes")]
// ...
[assembly: XmlnsDefinition("urn:foobar", "FoobarLibrary.Controls")]
// ...

It may work (I haven't tried). Your XAML will look like this:

<Window x:Class="FoobarProject.MainWindow"
    xmlns="urn:foobar"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

Note that you can't get rid of x namespace:

It isn't mapped to .NET namespace, it's pure XML namespace and part of XAML language.
Doing so would cause conflicts (x:Name vs. Name).

Speaking of conflicts, merging namespaces like this is asking for trouble. You are likely to run into name conflicts which these namespaces are designed to solve.

WPF XAML merge default namespace definitions

1 Answers