我收到一个错误：使用未分配的局部变量“艺术家”，不知道我在做什么错？

Question

private void btn_AddSongArtistPlaylist_Click(object sender, EventArgs e)
{
        Artist artist;

        if (cmbBox_AddSongPlaylistArtist.SelectedIndex == 0)
        {
            if (cmbBox_Artist.SelectedIndex == 0)
            {
                artist = new Artist(txtBox_NameArtist.Text, dateTP_BirthdatArtist.Value.Date);
            }
            else 
            {
                foreach (Artist a in Artists)
                {
                    if (a.Name == cmbBox_Artist.SelectedText)
                    {
                        artist = a;
                    }
                }
            }
            Song song = new Song(txtBox_Name.Text, Convert.ToInt32(txtBox_YearBirthday.Text), artist, txtBox_PathToFile.Text);
        }
    }

Answer 1

You are using the potentially unassigned variable artist . See:

private void btn_AddSongArtistPlaylist_Click(object sender, EventArgs e)
    {
        Artist artist;
        if (cmbBox_AddSongPlaylistArtist.SelectedIndex == 0)
        {
            if (cmbBox_Artist.SelectedIndex == 0)
            {
                artist = new Artist(txtBox_NameArtist.Text, dateTP_BirthdatArtist.Value.Date);
            }
            else 
            {
                foreach (Artist a in Artists)
                {
                    if (a.Name == cmbBox_Artist.SelectedText)
                    {
                        artist = a;
                    }
                }
            }
            Song song = new Song(txtBox_Name.Text, Convert.ToInt32(txtBox_YearBirthday.Text), artist, txtBox_PathToFile.Text); // right here!
        }
    }

If the second if statement evaluates to false , and there are no objects in the Artists collection, you will hit that new Song line with an unassigned variable. Try initializing artist to null .

private void btn_AddSongArtistPlaylist_Click(object sender, EventArgs e)
    {
        Artist artist = null;
        if (cmbBox_AddSongPlaylistArtist.SelectedIndex == 0)
        {
            if (cmbBox_Artist.SelectedIndex == 0)
            {
                artist = new Artist(txtBox_NameArtist.Text, dateTP_BirthdatArtist.Value.Date);
            }
            else 
            {
                foreach (Artist a in Artists)
                {
                    if (a.Name == cmbBox_Artist.SelectedText)
                    {
                        artist = a;
                    }
                }
            }
            Song song = new Song(txtBox_Name.Text, Convert.ToInt32(txtBox_YearBirthday.Text), artist, txtBox_PathToFile.Text); // now you're fine
        }
    }