Recently I tried changing the View of an XSLTListViewWebpart to a calendar view from code but it didnt work.

I tried it the same way as I did it for every other webpart, setting the ViewGuid property, but it kept using a normal list view of its events, which wasn’t even its default (which was the calendar). When I investigated the issue further I noticed something strange.

When setting the webpart’s View to the Calendar view from the GUI, it worked, but it also changed the webpart from an XsltListViewWebpart to an ordinary ListViewWebpart.

SPList list = ...
SPView view = ...

ListViewWebPart wp = new ListViewWebPart();
...
wp.ViewGuid = view.ID.ToString("B").ToUpper();

When I created a ListViewWebpart instance in code and set its View to the calendar view it now worked!