Coming from the iOS world where we have UIImageView and the property animationImages: http://developer.apple.com/library/ios/documentation/UIKit/Reference/UIImageView_Class/Reference/Reference.html#//apple_ref/occ/instp/UIImageView/animationImages
Where animationImages is just an array of arbitrary animation frames. You specify the images (maybe 15), then set the total animation time (maybe 4 seconds) in one of the other properties, then just start the anim and the images in animationImages will play sequentially over the specified time with an even frame rate.
How would I do the same with WP7/Silverlight? This all Expression Blend seems wonderful, but I just can't find a way to animate the image source (I'm guessing it might be impossible). How would I do the same? Should I add a unique image object for each frame in the animation, then play around with visibility/opacity properties and manually have to create all the spaced out key frames? That sounds like a lot of extra work + overhead and not a nice way to go...