In an unsorted DataGrid bound to a DataTable, you can get a reference to a row in the DataTable through the DataGrid.CurrentRowIndex.

DataTable dataTable = (DataTable) dataGrid1.DataSource;
DataRow dataRow = dataTable.Rows[ dataGrid1.CurrentRowIndex ];

But if the grid has been sorted, you can no longer get at the current row in the table through the grid's CurrentRowIndex. But for both unsorted and sorted grids, you can get at the current row through the BindingContext and the Current property of the BindingManagerBase.

BindingManagerBase bm =
  dataGrid1.BindingContextr[ dataGrid1.DataSource, dataGrid1.DataMember ];
DataRow dataRow = ( (DataRowView) bm.Current ).Row;

Contributed from George Shepherd's Windows Forms FAQ