Question

I am just going through the WPF concepts I came across these routed events ,dependency properties and attached events.
I think I am not able to understand the concepts behind them and why they were being called in the place of .net originated methods?

Answer 1

Routed Events provide the ability for different controls in the element tree to react to events.

For instance, if we have a Window containing a StackPanel containing a Button and someone presses the mouse key on the button, the events will be fired in this order:

PreviewMouseDown on Window
PreviewMouseDown on StackPanel
PreviewMouseDown on Button
MouseDown on Button
MouseDown on StackPanel
MouseDown on Window

These “preview” events use a behavior called Tunneling. The normal events Bubble up again.

If you set the Handled property of the EventArgs to true, the tunneling and bubbling will stop. Tunneling or Bubbling is called the Routing Strategy.

This enables handling a variety of situations, for instance:

• Preventing any child element of the StackPanel to receive mouse down events. (Set Handled to true on StackPanel.PreviewMouseDown).
• Handling key presses on a Window that have not been handled by any other control (Window.KeyDown)

I would advise not looking into Attached Events untill this becomes absolutely necessary. The scenario’s for attached events are very limited. Attached events are also routed events.