What you have to do is to set the MinimumHeight property of the row. Not only the Height property. That's the key. Put the code bellow in the CellPainting event of the datagridview
private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
foreach(DataGridViewRow x in dataGridView1.Rows)
{
x.MinimumHeight = 50;
}
}