title: WPF DataGrid content does not scroll
body: <p>After searching for a fix to this issue in the previous answers I've decided to post my example.
  I have the following situation: my datagrid is placed inside a Grid row that is itself placed inside a UserControl.The UserControls does not have a fixed height, as I want the control to resize together with the window. The datagrid is bound to a datasource. Needless to say that the Datagrid itself and its container(the Grid) do not have set a fixed height. My question is: how do I make the vertical scrollbar of the DataGrid to appear? </p>