Thank you for writing.
The SelectedPageChanging event will be fired, when the currently active page in RadPageView is being changed. For example when you click the tab of another page to activate it or when you set the SelectedPage property of the control. The Page in the event arguments will provide the page you are changing to. The currently selected page can be accessed via the SelectedPage property of the control.
The PageIndexChaning event will be fired, when a page in the Pages collection changes its index. For example if you insert some page or swap pages. The CurrentIndex and the NewIndex will tell you which was the index the Page was, and which is the NewIndex the page will have.
So these events cover different cases.
Note taken about the API description. I have updated your Telerik Points
for this report.
I hope that this clear things up. Let me know if you have any additional questions regarding this matter.
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