Oznaciti pronađene rezultate u datagridview kontroli

Code:

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            foreach (DataGridViewRow dgvr in dataGridView1.Rows)
            {
                if (dgvr.Cells[0].Value is string && ((string)dgvr.Cells[0].Value).Contains(textBox1.Text))
                    dgvr.DefaultCellStyle.BackColor = Color.Red;
                else
                    dgvr.DefaultCellStyle.BackColor = Color.White;
            }
        }