In XAML, when you want to reference a CLR type, you have to add a namespace mapping that maps the XML namespace to the CLR namespace, like so:
xmlns:local="clr-namespace:MyTestApp.Controls;assembly=TestApp.Controls"
However the Types from PresentationFramework and PresentationCore are included differently, like so:
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
What I like about this declaration is the fact that it hides all the CLR-namespaces that are automatically imported. This is possible because inside PresentationFramework.dll (and some in PresentationCore.dll), we have a bunch of assembly attributes, namely the XmlnsDefinitionAttribute:
[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows")] [assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Data")] [assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Navigation")] [assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Shapes")] [assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Documents")] [assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "System.Windows.Controls")]
This does the mapping from the CLR namespace to the XML namespace. So instead of having a list of xmlns mappings in your XAML file, you just have one, of the formxmlns:x=“http://schemas.microsoft.com/winfx/2006/xaml/presentation”. This not only simplifies the mapping declarations but it is also easier to remember. So say for example your company created a bunch of cool WPF controls; you could then have a XmlnsDefinitionAttribute in the Control Library as:
[assembly: XmlnsDefinition("http://www.my-company.com/wpf", "MyCompany.Controls")]
Then your users could use these controls in their XAML files simply by including the namespace mapping:
xmlns:mc="http://www.my-company.com/wpf"
Now isn’t that a cooler way of declaring the XML namespace!