private void DataGridView_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
{
if (e.Button == MouseButtons.Right && e.RowIndex > -1 && e.ColumnIndex > -1)
{
dataGridView1.ClearSelection();
dataGridView1.CurrentRow.Selected = false;
dataGridView1.Rows[e.RowIndex].Selected = true;
}
}