Markup Extensions for Events in .Net 4.5

Question

WPF does not define a markup extension to be used for events, third parties are able to create a markup extension that can be used with events. Now WPF 4.5 supports markup extensions for events. Can anyone help how to achieve this in .Net 4.5 with an elegant example?

Answer 1

Event markup extensions allow you to use markup extensions for events, where up until WPF 4.5 they were only available for properties. For example:

<Canvas ClipToBounds="True" Background="White"
        MouseLeftButtonDown="{local:EventToCommand StartPaintCommand}"
        MouseMove="{local:EventToCommand AddLineCommand}"
        MouseLeftButtonUp="{local:EventToCommand EndPaintCommand}">
</Canvas>

A complete example can be found here.

Answer 2

Command

{eb:EventBinding} (Simple naming pattern to find Command)

{eb:EventBinding Command=CommandName}

CommandParameter

$e (EventAgrs)

$this or $this.Property

string

https://github.com/JonghoL/EventBindingMarkup

Answer 3

Here is an example of a very versatile markup extension I wrote that can bind events directly to methods on your view model:

http://www.singulink.com/CodeIndex/post/building-the-ultimate-wpf-event-method-binding-extension

Usage:

<!--  Basic usage  -->
<Button Click="{data:MethodBinding OpenFromFile}" Content="Open" />

<!--  Pass in a binding as a method argument  -->
<Button Click="{data:MethodBinding Save, {Binding CurrentItem}}" Content="Save" />

<!--  Another example of a binding, but this time to a property on another element  -->
<ComboBox x:Name="ExistingItems" ItemsSource="{Binding ExistingItems}" />
<Button Click="{data:MethodBinding Edit, {Binding SelectedItem, ElementName=ExistingItems}}" />

<!--  Pass in a hard-coded method argument, XAML string automatically converted to the proper type  -->
<ToggleButton Checked="{data:MethodBinding SetWebServiceState, True}"
                Content="Web Service"
                Unchecked="{data:MethodBinding SetWebServiceState, False}" />

<!--  Pass in sender, and match method signature automatically -->
<Canvas PreviewMouseDown="{data:MethodBinding SetCurrentElement, {data:EventSender}, ThrowOnMethodMissing=False}">
    <controls:DesignerElementTypeA />
    <controls:DesignerElementTypeB />
    <controls:DesignerElementTypeC />
</Canvas>

    <!--  Pass in EventArgs  -->
<Canvas MouseDown="{data:MethodBinding StartDrawing, {data:EventArgs}}"
        MouseMove="{data:MethodBinding AddDrawingPoint, {data:EventArgs}}"
        MouseUp="{data:MethodBinding EndDrawing, {data:EventArgs}}" />

<!-- Support binding to methods further in a property path -->
<Button Content="SaveDocument" Click="{data:MethodBinding CurrentDocument.DocumentService.Save, {Binding CurrentDocument}}" />

View model method signatures:

public void OpenFromFile();
public void Save(DocumentModel model);
public void Edit(DocumentModel model);

public void SetWebServiceState(bool state);

public void SetCurrentElement(DesignerElementTypeA element);
public void SetCurrentElement(DesignerElementTypeB element);
public void SetCurrentElement(DesignerElementTypeC element);

public void StartDrawing(MouseEventArgs e);
public void AddDrawingPoint(MouseEventArgs e);
public void EndDrawing(MouseEventArgs e);

public class Document
{
    // Fetches the document service for handling this document
    public DocumentService DocumentService { get; }
}

public class DocumentService
{
    public void Save(Document document);
}