you can do that on RowAdded Event :
_data_grid_view.RowsAdded += new System.Windows.Forms.DataGridViewRowsAddedEventHandler(this._data_grid_view_RowsAdded);
private void _data_grid_view_RowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
{
_data_grid_view.Rows[e.RowIndex].Height = 42;
}
when a row add to the dataGridView it just change it height to 42.