是否有可能在mvvm模式中获取wpf datagrid上的动态列？

Im developing a product in wpf (mvvm pattern). I have a scenario in which i have spent more than a week for no good result. Pls help me if you can... Here is the scenario, according to the user's customization(user ll select the columns) i have to display a set of data into datagrid. Currently im binding a ObservableCollection with set of properties to the itemsource of datagrid. This limits me to fixed column size. Note: The n number of columns name is listed out for user's selection. If its done in code behind it is easy by "datagrid.columns.add()". Can any one out there help me in this scenario.Im developing a product in wpf (mvvm pattern).