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

Debugging Animations

Common Errors

If you get the following error: Cannot animate '(0).(1)' on an immutable object instance. it could be that you are run into one of the following limitations:

• You are animating a dependency property without setting a local value
• You are animating a dependency property who's current value is defined in another assembly that is not merged into the resource dictionary.
• You are animating a value that is currently databound

Answer 2

Use of Non-Default Constructors with x:Arguments

In XAML 2006 objects must have a public default constructor to use them. In XAML 2009 you can pass constructor arguments by using the x:Arguments syntax.

<!-- XAML 2006 -->
<DateTime>00:00:00.0000100</DateTime>

<!-- XAML 2009 -->
<DateTime>
    <x:Arguments>
        <x:Int64>100</x:Int64>
    </x:Arguments>
</DateTime>

Answer 3

Easy Object References with {x:Reference}

If you want to create an object reference today you need to do a databinding and declare the source with an ElementName. In XAML 2009 you can use the new {x:Reference} markup extension

<!-- XAML 2006 -->
<Label Target="{Binding ElementName=firstName}">FirstName</Label>
<TextBox x:Name="firstName" />

<!-- XAML 2009 -->
<Label Target="{x:Reference firstName}">FirstName</Label>
<TextBox x:Name="firstName" />

Answer 4

Set a ValidationError by Code

A ValidatioRule in a BindingExpression only triggers, when the target side of the binding changes. If you want to set a validation error by code you can use the following snippet.

Set the validation error

ValidationError validationError = 
    new ValidationError(regexValidationRule, 
    textBox.GetBindingExpression(TextBox.TextProperty));

validationError.ErrorContent = "This is not a valid e-mail address";

Validation.MarkInvalid(
    textBox.GetBindingExpression(TextBox.TextProperty), 
    validationError);

Clear the validation error

Validation.ClearInvalid(textBox.GetBindingExpression(TextBox.TextProperty));

Answer 5

Markup extensions and attached properties are my favorite features, they enable you to extend XAML "vocabulary" in a very elegant way.

Markup extensions

<!-- Binding to app settings -->
<CheckBox IsChecked="{my:SettingBinding MinimizeToTray}">Close to tray</CheckBox>

<!-- Fill ItemsControl with the values of an enum -->
<ComboBox ItemsSource="{my:EnumValues sys:DaysOfWeek}"/>

<!-- Localization -->
<TextBlock Text="{my:Localize HelloWorld.Text}"/>

<!-- Switch on the result of a binding -->
<TextBlock Text="{my:Switch Path=IsGood, ValueIfTrue=Good, ValueIfFalse=Bad}"/>

Attached properties

<!-- Sort GridView automatically -->
<ListView ItemsSource="{Binding Persons}"
      IsSynchronizedWithCurrentItem="True"
      util:GridViewSort.AutoSort="True">
    <ListView.View>
        <GridView>
            <GridView.Columns>
                <GridViewColumn Header="Name"
                                DisplayMemberBinding="{Binding Name}"
                                util:GridViewSort.PropertyName="Name"/>
                <GridViewColumn Header="First name"
                                DisplayMemberBinding="{Binding FirstName}"
                                util:GridViewSort.PropertyName="FirstName"/>
                <GridViewColumn Header="Date of birth"
                                DisplayMemberBinding="{Binding DateOfBirth}"
                                util:GridViewSort.PropertyName="DateOfBirth"/>
            </GridView.Columns>
        </GridView>
    </ListView.View>
</ListView>


<!-- Vista Glass effect -->
<Window x:Class="WpfApplication1.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:my="clr-namespace:WpfApplication1"
        Title="Window1"
        my:WinUtil.EnableAeroGlass="True">

...

Source for GridViewSort (btw, it uses the GridViewColumnHeader.Click event mentioned by Ortus)

Answer 6

Grid size sharing (here's a good example). Long story short you can have grid columns and rows share sizes, even across different grids. This will be invaluable for all the people out there who are using DataGrids without the need to edit the data in place.