Hidden features of WPF and XAML?

Question

Here is a large number of hidden features discussed for variety of languages. Now I am curious about some hidden features of XAML and WPF?

One I have found is the header click event of a ListView

<ListView x:Name='lv' 
      Height="150" 
      GridViewColumnHeader.Click="GridViewColumnHeaderClickedHandler">

The GridViewColumnHeader.Click property is not listed.

Some of relevant features so far:

• Multibinding combined with StringFormat

• TargetNullValue to bindings

• TextTrimming property

• Markup extensions

• Adding Aero effect to Window

• Advanced "caption" properties

• XAML Converters

See also:

1. Hidden features of C#
2. Hidden features of Python
3. Hidden features of ASP.NET
4. Hidden features of Perl
5. Hidden features of Java
6. Hidden features of VB.NET
7. Hidden features of PHP
8. Hidden features of Ruby
9. Hidden features of C
10. And So On........

Answer 1

PriorityBinding. Allows you to use asyn bindings in an "first come first show" order:

<TextBlock.Text>
      <PriorityBinding FallbackValue="defaultvalue">
        <Binding Path="SlowestDP" IsAsync="True"/>
        <Binding Path="SlowerDP" IsAsync="True"/>
        <Binding Path="FastDP" />
      </PriorityBinding>
</TextBlock.Text>

Answer 2

There is also PresentationTraceSources.TraceLevel trick to debug what is going on with bindings in any particular scenario. All you have to do is to reference System.Diagnostics namespace in WindowsBase assembly

xmlns:sd="clr-namespace:System.Diagnostics;assembly=WindowsBase"

and then add following to the binding expression:

<TextBlock Text="{Binding Message, sd:PresentationTraceSources.TraceLevel=High}"  />

Log will be like this:

System.Windows.Data Warning: 52 : Created BindingExpression (hash=5923895) for Binding (hash=7588182)
System.Windows.Data Warning: 54 :   Path: 'Message'
System.Windows.Data Warning: 56 : BindingExpression (hash=5923895): Default mode resolved to OneWay
System.Windows.Data Warning: 57 : BindingExpression (hash=5923895): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 58 : BindingExpression (hash=5923895): Attach to System.Windows.Controls.TextBlock.Text (hash=65248697)
System.Windows.Data Warning: 63 : BindingExpression (hash=5923895): Resolving source 

Answer 3

XAML Converters

The following list shows converters developed by the WPF community to convert different formats to XAML or vice versa.

Adobe Illustrator XAML Export Plugin

Adobe Photoshop to XAML Converter

Blender XAML Export Plugin

Lightwave XAML Export Plugin

Visio XAML Export

3D Studio Max to XAML Converter

Maya to XAML Converter

Flash to XAML Converter

SVG to XAML Converter

WMF/EMF to XAML Converter

Answer 4

Not really a hidden feature but with WPF/XAML you get Bea Stollnitz and Josh Smith. Queen and King of WPF/XAML programming.

Answer 5

Support for Arbitrary Dictionary Keys

In XAML 2006 all explicit x:Key value were treated as strings. In XAML 2009 you can define any type of key you like by writing the key in ElementSyntax.

<!-- XAML 2006 -->
<StreamGeometry x:Key="CheckGeometry">M 0 0 L 12 8 l 9 12 z</StreamGeometry>

<!-- XAML 2009 -->
<StreamGeometry>M 0 0 L 12 8 l 9 12 z
    <x:Key><x:Double>10.0</x:Double></x:Key>
</StreamGeometry>

Answer 6

Generics in XAML with x:TypeArguments

If you want to use an ObservableCollection in XAML you need to create a type that derives from ObservableCollection because you cannot declare it in XAML. With XAML 2009 you can use the x:TypeArguments attribute to define the type of a generic type.

<!-- XAML 2006 -->
class EmployeeCollection : ObservableCollection<Employee>
{
}

<l:EmployeeCollection>
    <l:Employee FirstName="John" Name="Doe" />
    <l:Employee FirstName="Tim" Name="Smith" />
</lEmployeeCollection>

<!-- XAML 2009 -->
<ObservableCollection x:TypeArguments="Employee">
    <l:Employee FirstName="John" Name="Doe" />
    <l:Employee FirstName="Tim" Name="Smith" />
</ObservableCollection />