You may already know this trick...
When you know how to do something directly in Excel and you want to achieve the same programatically, you can make a good usage of the macro recorder (in developer tools, see first screenshot). After that, you have to translate the VBA macros into C# using interop Excel but if you know a little bit of VB that should not be difficult.
Then for your question I recorded the action to drag and drop a column field to the rows section. Thanks to the macro recorded it seems that you can achieve that by picking up the targeted field object and change its properties Orientation and Position.