How Dispose for UX element triggered?

Dear Sirs,

I have large-size made with fuse and i have a serious problem with memory, Then try to use MemoryPolicy for images with ‘QuickUnload’ value while the videos doesn’t have match. So in general how do you trigger the Dispose method for IDisposable ?

I’d like to dispose everything not visible even or not important and to keep in mind while i’m using ScrollView