Legacy modal site pages
The context.ShowModalSitePage() is no longer used, so existing custom code that called this API will no longer compile or run. Any layouts that use this call must be adjusted manually to have a floating region placed using the PlaceRegion() API.
Also, the ModalSitePageClosed event handler has been removed, and existing custom code that tries to add this handler will no longer compile or run.
Public Overrides Sub OnScriptInitializing(ByVal context As
		MLLScriptInitializingContextI, ByVal parms As MLLScriptInitializingParmsI)
	 	AddHandler ModalSitePageClosed, AddressOf OnModalSitePageClosed
End Sub
	Public Sub OnModalSitePageClosed(ByVal context As
		MLLModalSitePageClosedContextI, ByVal parms As MLLModalSitePageClosedParmsI)
	End Sub 
	  
      The 
		AddHandler and 
		Public Sub OnModalSitePageClosed() lines in bold above
		are automatically removed when the 
		OnScriptInitializing() handler has no code in it,
		meaning it was not actually used. If the 
		OnScriptInitializing () has code, it is not
		automatically removed. Instead, the script fails to compile, and it must be
		removed manually as part of the work to remove calls to 
		ShowModalSitePage().