Typical "Identifier not found" with class variable

You can just go:

Type Tileset
	Field lstTiles:TList = New TList	

	Method addTile (t:Tile)
		lstTiles.AddLast(t)
	End Method
End Type

Theres no need for the extra code when doing one type per instance. The extra stuff is only needed for Globals, and Mark is planning on fixing that too.