This delegate specifies the parameter list that a subroutine must
have to handle the DataGrid.SortCommand event.
This event specifies additional information about the selected column
(DataGridSortCommandEventArgs.SortExpression),
which you can use to build a new data source. This event handler
should then rebind the data source to the DataGrid
control to update the display.
public delegate void DataGridSortCommandEventHandler(object source, DataGridSortCommandEventArgs e);
