Tim Van Wassenhove

Here is a way that allows the user to select a row (custom object properties are used as column values) from a DataGridView assuming that the SelectionMode property is set FullRowSelect:

private void FillDataGridViewPersons( List<person> persons ) {
 this.dataGridViewPersons.Rows.Clear();

 for ( int i = 0; i < persons.Count; ++i ) {
  this.dataGridViewPersons.Rows.Add();
  this.dataGridViewPersons.Rows[i].Tag = persons[i];
  this.dataGridViewPersons.Rows[i].SetValues( new object[] { persons[i].Id, persons[i].Name } );
 }
}

private void buttonDoSomething_Click( object sender, EventArgs e ) {
 if ( this.dataGridViewPersons.SelectedRows.Count == 1 ) {
  int selectedRowIndex = this.dataGridViewPersons.SelectedCells[0].RowIndex;
  Person selectedPerson = (Person)this.dataGridViewPersons.Rows[selectedRowIndex].Tag;
  MessageBox.Show( String.Format( "You selected the person with id: {0}", selectedPerson.Id ) );
 }
}