c# - 错误 : (using List class) Index was outside the bounds of array

Question

我正在做一个项目，我是 c# 编程的初学者，但不知何故，我遇到了一个我无法解决的问题。它是如何发生的:在执行代码时，应用程序成功启动但出现异常显示“索引超出数组范围”。之后，我能够单击列表框中的项目，它会在文本框中显示第二个对象。所以......它似乎有效(点击列表框的项目)但我无法弄清楚为什么它会抛出关于数组的异常。下面是我的当前代码。

**更新:我真诚地道歉。我上传了错误的代码。应该是这段代码:

代码:

struct studentInfo
{  
  public string studentID;
  public string major;
}  

public partial class Form1 : Form
{
    private List<studentInfo> studentList = new List<studentInfo>();

    public Form1()
    {
        InitializeComponent();
    }


    private void ReadInputFile()
    {
        try
        {
            StreamReader inputFile;
            string line = "";

            studentInfo student = new studentInfo();

            char[] delimiter = { ',' };

            inputFile = File.OpenText("Student Info.txt");

            while (!inputFile.EndOfStream)
            {
                line = inputFile.ReadLine();

                string[] token = line.Split(delimiter);

                student.studentID = token[0];
                student.major = token[1];

                studentList.Add(student);

            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
    private void DisplaystudentID()
    {
        foreach (studentInfo student in studentList)
        {
            studentInfoListBox.Items.Add(student.studentID);
        }
    }

    private void DisplayNames()
    {

    }
    private void button1_Click(object sender, EventArgs e)
    {
        ReadInputFile();

        DisplaystudentID();
    }

    private void studentInfoListBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        int index = studentInfoListBox.SelectedIndex;

        majorTextBox.Text = studentList[index].major;


    }

    private void button3_Click(object sender, EventArgs e)
    {
        Application.Exit();
    }
}

Answer 1

我的猜测是 SelectedIndexChanged 在开始时运行(在您选择任何内容之前)并且此时 nameListBox.SelectedIndex 将为 -1 并且您无法在列表中获得“负 1 位置的项目”。我会确保所选索引有效

https://msdn.microsoft.com/fr-fr/library/system.windows.forms.listbox.selectedindex(v=vs.110).aspx“当前所选项目的从零开始的索引。如果未选择任何项目，则返回负一 (-1) 值。”

我会这样修改代码:

private void nameListBox_SelectedIndexChanged(object sender, EventArgs e)
{
    int index = nameListBox.SelectedIndex;
    if(index !=-1)
    {
        phoneLabel.Text = phoneList[index].phone;
    }
    // else do nothing, the selected item didn't really change, it's just called for the first time, think of it as the control saying "hey i just got created and i'm notifying you that the selected item is now nothing"
}