1.Show/Hide columns:
Use Column.Visible property to hide/show column.
You can see the Grid Stylizing sample, right click on column header for attached to column context menu and choose some command, you can see Hide column, Show all columns commands in this menu
2.Show/hide nodes:
Use NodeBase.Hidden property to show/hide node.
See the TreeView Reaplcement sample to know how to hide nodes at runtime, select node to hide and click Hide selected button. To show hidden nodes click Show hidden nodes button.