Behaviors add interactivity to your application without having to write any code.
They are reusable pieces of packaged code that can be dragged onto any object to change its own or
other object’s properties,control storyboards ,change layout properties etc..
Behaviors not necessarily be invoked by triggers,they work when some conditions are met.
An Action is an object that can do something..
A Trigger reacts to the cause and invokes one or more Actions.
Expression Blend 3 provides by default some behaviors and Actions in the asset panel…..
Here are some examples:
1) ControlStoryBoardAction: Lets u play,start,stop,pause a storyboard.
Here the storyboard animates the width property of a rectangle on click event of Button.
You have to drag the ControlStoryBoardAction on to your button and set the properties.
2) ChangePropertyAction: Changes the property and lets u animate it over some duration.
Here the opacity of the ellipse varies on click of the button.
Drag the action on button and set the properties.
There are options available to ease in and ease out your animation…over time.
3) FluidMotionBehaviour: Animates the layout properties of objects in panel.
Here the button flies in from left in the canvas which is its parent container.
You can set the direction of easing in/out in x and y direction with options available in properties panel
4) MouseDragElementBehaviour: It lets the object within the parent container to reposition.
Here the ellipse can be dragged within the boundaries of the button.
5) GotoStateAction: Changes to visual state
Here the rectangle and ellipse colliding animation is captured by a state.
This state is transitioned to on click event of a button.
You can also get more behaviors from the Expression Studio site.
Navigate to Expression Gallery to find more behaviors.