Question

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
        checkxml();
    }

    private void Form2_Load(object sender, EventArgs e)
    {

    }
    private void Form2_FormClosing(object sender, FormClosingEventArgs e)
    {
        Environment.Exit(0); 
    }

    private void displayMessageBox(object sender, FormClosingEventArgs e)
    {
    }


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

    private void button1_Click(object sender, EventArgs e)
    {           
        Form3 form3 = new Form3();
        form3.Show();

    }

    private void button2_Click(object sender, EventArgs e)
    {
        XmlDocument xDoc = new XmlDocument();
        xDoc.Load("mp3spelers.xml");
        string text = listBox1.GetItemText(listBox1.SelectedItem);
        foreach (XmlNode xNode in xDoc.SelectNodes("Players/Player"))
        {
            if (xNode.SelectSingleNode("make").InnerText == text) xNode.ParentNode.RemoveChild(xNode);
            xDoc.Save("mp3spelers.xml");
        }
    }

     public  List<string> _items = new List<string>();

    public void checkxml()
    {

        string[] arr = XDocument.Load("mp3spelers.xml").Root
                       .Descendants("make")
                       .Select(make => (string)make)
                       .ToArray();
        for (int i = 0; i < arr.Length; i++)
        {
            _items.Add(arr[i]);
        }

        listBox1.DataSource = _items;
    }

    public int indexnumber;

    private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
    {          
        indexnumber = listBox1.SelectedIndex;
        loadListBox(indexnumber, 0, "load");                       
    }


    public void loadListBox(int index, int mutatie, string action)
    {
        List<string> _modle = new List<string>();
        string[] arr1 = XDocument.Load("mp3spelers.xml").Root
                      .Descendants("modle")
                      .Select(modle => (string)modle)
                      .ToArray();

        List<string> _mbstorage = new List<string>();
        string[] arr2 = XDocument.Load("mp3spelers.xml").Root
                      .Descendants("mbstorage")
                      .Select(mbstorage => (string)mbstorage)
                      .ToArray();

        List<string> _price = new List<string>();
        string[] arr3 = XDocument.Load("mp3spelers.xml").Root
                      .Descendants("price")
                      .Select(price => (string)price)
                      .ToArray();
        List<string> _storage = new List<string>();
        string[] arr4 = XDocument.Load("mp3spelers.xml").Root
                      .Descendants("storage")
                      .Select(storage => (string)storage)
                      .ToArray();


        switch (action)
        {
            case "load":                    
                textBox1.Clear();
                textBox1.Text = "Model: " + arr1[index] + "\r\n" + "Opslag in MB: " + arr2[index] + "\r\n" + "Prijs: " + arr3[index] + "\r\n" + "Voorraad: " + arr4[index];
                break;
            case "mutate":
                int indexnumber = listBox1.SelectedIndex;
                int mutatienummer = Convert.ToInt32(arr4[indexnumber]);
                int mutatienummer2 = mutatienummer + mutatie;

                            XmlDocument xDoc = new XmlDocument();
                            xDoc.Load("mp3spelers.xml");
                            string text = arr4[indexnumber];
        foreach (XmlNode xNode in xDoc.SelectNodes("Players/Player"))
        {
            if (xNode.SelectSingleNode("storage").InnerText == text)

            xDoc.Save("mp3spelers.xml");
        }


                break;
        }
    }

    private void infoToolStripMenuItem_Click(object sender, EventArgs e)
    {
        listBox1.Hide();
        button1.Hide();
        button2.Hide();
        button3.Hide();
        textBox1.Clear();
        textBox1.Text = "Soundsharp";
    }

    private void mP3SpelersToolStripMenuItem_Click(object sender, EventArgs e)
    {
        listBox1.Show();
        button1.Show();
        button2.Show();
        button3.Show();
    }

    private void button3_Click(object sender, EventArgs e)
    {
        Form4 form4 = new Form4();
        form4.Show();
    }

    private void button4_Click(object sender, EventArgs e)
    {
        listBox1.SelectedIndex = 0;
        listBox1.DataSource = null;
        checkxml();
        listBox1.SelectedIndex = 1;

    }
}
}

当我尝试从textbox为selectedindex分配值但selectedindex为0 / -1并且崩溃程序时，我收到错误，所以我尝试做的是在刷新按钮（按钮4）上分配selectedindex但似乎无法正常工作。

类型＆＃39; System.IndexOutOfRangeException＆＃39;的例外情况发生了

在尝试通过textbox关闭indexnumber来listbox向{{1}}分配值时，案例加载发生错误，因此它知道所选内容。

Answer 1

第1步：如果LisBox选择的索引中没有项目为-1

替换它：

listBox1.SelectedIndex = 0;

有了这个：

listBox1.SelectedIndex = -1;

第2步：，同时获取selctedindex值，首先检查是否有任何选定的项目

替换它：

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{          
    indexnumber = listBox1.SelectedIndex;
    loadListBox(indexnumber, 0, "load");                       
}

用这个：

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{          
    if(listBox1.SelectedIndex >= 0)
    {
      indexnumber = listBox1.SelectedIndex;
      loadListBox(indexnumber, 0, "load");                       
    }
}

Answer 2

如果selectedindex为0，则选择第一个元素，如果为-1，则不选择任何元素。如果您尝试在位置-1处访问数组，则应该只获得IndexOutOfRangeException。

第一步是检查所选索引是否为-1，以及是否尝试访问该位置的数组。

在选择更改的事件处理程序中设置断点，并查看是否多次调用它。

Selectedindex在列表框中为0 / -1

2 个答案: