So, today we will see to how to crop an image in expression tool. Cropping an image in Expression Blend is way to easy. Lets dig in...
1. Create a Blank Windows Phone Silverlight app.
2. Select an image from your library and drag it in to your expression blend workplace. Now we will crop this image.
2. To crop the image i need a clipping mass, it could be rectangle, ellipse or line. I am choosing rectangle.
 3. Here it is. Now here you see a rectangle that I have used to crop I want the rectangle area to fill my image and to remove other part of image as transparent.
 4. First of all, I need to make the rectangle's color to empty so that I can see then image in background.  To do so I change it's opacity 0.
 5. Now to crop the image you have to make it a clipping path. Like this:
 6. Select the image you want to crop.
 7. Here is your cropped image.You can crop it in any shape. You can also use ellipse to crop images round.
Happy Development :)