I already answered to this question the other thread you have opened. I will summarize the discussion here so that others from the community will be able to find this information.
With the current version of the implementation of the wrappers and the UI for Xamarin suite of controls there is no way to utilize a LoadOnDemand functionality. We cannot expose this feature in our next official release as well because we are in a freeze period now. This means the feature will not be available in our Q1 2016 release. We will consider its implementation for our future releases.
As an alternative to the automatic loading of items users are capable of manually loading a number of items whenever the end user requires. This can be achieved with a simple button. In the Click handler customers can update the bound RadListView.ItemsSouce collection.
Pavel R. Pavlov
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