Non invocable member

private void Form1_Load(object sender, EventArgs e)
{
    dataGridView1.Rows.Add(5);
}

private void dataGridView1_CellContentClick(object sender, 
    DataGridViewCellEventArgs e)
{
}
private void dataGridView1_MouseDown(object sender, 
    System.Windows.Forms.DataGridViewCellMouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Right)
    {
        foreach (DataGridViewRow row in dataGridView1.SelectedRows)
        {
            row.Selected = false;
        }
        dataGridView1.Rows(e.RowIndex).Selected = true;
    }
}