Question

我想从列表中删除一个项目......

我显然错过了一些东西......我已经尝试了几乎所有的变化，包括EXCEPT，REMOVE等......

调试时，我会逐步浏览每个ling，但是当它到达btnRemove_Click时，它会逐步删除但不删除任何内容......就好像我从未发送命令删除任何内容一样???

帮助！

public partial class frmUpdate : Form
{
    private Student student = new Student();
    private string _scores;

    public frmUpdate()
    {
        InitializeComponent();
    }

    public string GetUpdatedScores(Student s)
    {
        txtName.Text = s.Name;
        _scores = s.Scores;        
        FillStudentGrades();
        this.ShowDialog();
        return _scores;


    }

    private void FillStudentGrades()
    {
        lstScores.Items.Clear();
        string[] grades = splitGrades(_scores);
        foreach (string s in grades)
        {
            lstScores.Items.Add(s.ToString());
        }       
    }

    private void lstScores_SelectedIndexChanged(object sender, EventArgs e)
    {
        int i = lstScores.SelectedIndex;
    }

    private void btnAdd_Click(object sender, EventArgs e)
    {
        frmAddScore addScore = new frmAddScore();
        _scores += " " + addScore.AddScore();
        FillStudentGrades();
    }

    private void btnUpdate_Click(object sender, EventArgs e)
    {
        int i = lstScores.SelectedIndex;

    }

    private void btnRemove_Click(object sender, EventArgs e)
    {
        int i = lstScores.SelectedIndex;

    }

    private void btnRemove_Click(object sender, EventArgs e)
    {
        if (lstScores.SelectedIndex < 0)
        {
            MessageBox.Show("You Must Select A Grade.");
            btnUpdate.Focus();
        }
        else
        {
            int i = lstScores.SelectedIndex;
            string[] grades = splitGrades(_scores);
            string message = "Are you sure you want to remove " + grades[i].ToString() + "?";
            DialogResult button = MessageBox.Show(message, "Confirm Remove",
                MessageBoxButtons.YesNo);
            if (button == DialogResult.Yes)
            {
                int count = 0;
                foreach (char c in grades[i])
                {
                    if (char.IsDigit(c))
                    {
                        count++;
                    }
                }
                int a = _scores.IndexOf(grades[i].ToString());
                _scores = _scores.Remove(a, (count + 1));
                FillStudentGrades();
                btnOk.Focus();
            }
            else
            {
                btnOk.Focus();
            }
        }
    }

    private void btnClearAll_Click(object sender, EventArgs e)
    {

    }

    private void btnOk_Click(object sender, EventArgs e)
    {
        student.Name = txtName.Text;
        student.Scores = _scores;
        this.Close();
    }

    private void btnExit_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    public string[] splitGrades(string s)
    {
        string[] grades = s.Split(' ');
        return grades;
    }
}

Answer 1

在C＃中，字符串是不可变的。 _scores.Remove(i);不会更改_scores。相反，它返回一个新的字符串对象，您可以将其分配给变量，例如，返回_scores，如下所示：

_scores = _scores.Remove(i);

Answer 2

你需要使用RemoveAt方法 - 因为你试图删除索引而不是值

从字符串列表中删除字符串时出现问题

2 个答案: