C＃my rich textbox不断添加所有歌曲名称，而不仅仅是1

Question

我正在为学校制作一个小小的音乐节目，并且我在我的richtextbox（rtb）中遇到了问题，它一直在添加以前的所有歌曲，我不知道如何修复它而不清理我每次点击按钮都会一遍又一遍。

private void AddSongKtab()
{
    SongKtab[nr] = new SongInfo();

    string m_SongName;
    string m_SongLocation;

    ofdOpenKtab.ShowDialog();

    m_SongName = ofdOpenKtab.SafeFileName;
    m_SongLocation = ofdOpenKtab.FileName;

    SongKtab[nr].SongName = m_SongName;
    SongKtab[nr].SongLocation = m_SongLocation;

    tbAddKtab.Text = "";

    tbAddKtab.Text = m_SongName;

    rtbExtraKtab.AppendText("added" + m_SongName + "\n");
    rtbExtraKtab.AppendText("Located at " + m_SongLocation + "\n\n");

    rtbSongsKtab.ScrollToCaret();

    nr++;

    showAllKtab();
}

private void showAllKtab()
{
    int m_index;

    rtbExtraKtab.Clear();

    for (m_index = 0; m_index < nr; m_index++)
    {
        rtbSongsKtab.AppendText(SongKtab[m_index].SongName + "\n");
    }
}