c# - この挿入コマンドでの重複を防止

Question

private void Save_Click(object sender, EventArgs e)
{
    if (idTextBox.Text != "" & nameTextBox.Text != "")
    {
        conn.Open();
        cmd.CommandText = "insert into item_details (id, Name, MFD, EXP, QTY, damaged, MP, CP) values ('" + idTextBox.Text + "','" + nameTextBox.Text + "','" + MFDTextBox.Text + "','" + EXPTextBox.Text + "','" + QTYTextBox.Text + "','" + damagedTextBox.Text + "','" + MPTextBox.Text + "','" + CPTextBox.Text + "')";
        cmd.ExecuteNonQuery();
        cmd.Clone();
        MessageBox.Show("record inserted");
        conn.Close();
    }
    Admin_welcome newChild = new Admin_welcome();
    newChild.MdiParent = MdiParent;
    newChild.Show();
    this.Hide();
}