How to pick image from gallery in xamarin forms.

I have created one layout Main.axml and placed a imageview and button in it for selecting

images from gallery and display in the image view.. it works .But

I want to use this in one of my forms ,for example: Expense.xaml .How will i use that layout in my form ,in a button click or something?Please help.

Or please suggest another way to pick  image from gallery using xamarin .