I use VisualStudio 2013, but I have an older version of Syncfusion (Essential Studio 10.3.0.43 ), which is probably the main problem.
I can't try upgrading until next week, but after that maybe everything will work OK.
Anyway, I got a XAML parsing exception trying to run your example directly.
Then I tried just revising my code to use the Command and CommandTarget on the exportEventsButton, as your sample does, but I could not get it to accept the <syncfusion.LayoutControl.GridView> element, even though I have Syncfusion.SampleLayout reference loaded.
I tried just executing the code in the ExportAllToCSV method in my button click method, but then I got the 'No entry point found' error shown in attached JPG.
In case it helps, I attached the relevant xaml and xaml.cs files I'm using.
'runDataGrid' is name of GridDataControl and 'exportEventsButton' is the button, obviously.
Attachment:
ExportCSV_6643b6b7.7z