How to know whether scroll rect has reached the end?

I am creating a dynamic list which pulls data from server, There are more than thousand items to be listed from server, so i decided to load only 50 items at the beginning and later if the user scrolls to the end, will add another 50 items to list and so on.

Hope this will avoid the initial loading and also if the user is not scrolling down to 50th item, it is not necessary to load the item.

But i do not know how to get it done ;( Either i should know the no of item in view or should know whether the scroll rect reached the end.

If you have any idea please share :)

I am using GridLayout Group with content size fitter to dynamically increase the size of container.

Thanks,