Question

我在form1上有一个按钮来执行此操作：

private void button1_Click(object sender, EventArgs e)
{
    int numberOfStudentsInClass;
    if (!int.TryParse(txtBoxNoS.Text, out numberOfStudentsInClass))
    {
        MessageBox.Show("Please enter the number of students in the class", "Alert", MessageBoxButtons.OK);
        return;
    }

    _allStudentsArray = new Student[numberOfStudentsInClass];
    form3.Show();
    form3.lblClass.Text = string.Format("Class {0}", comboBox1.Text);
    form3.lblNoOfS.Text = numberOfStudentsInClass.ToString();
}

form3正确地将正确的整数和字符串传递给此函数：

public void addStudent(string sn, string tp, string tw, string gc, string gp, string gg, string t, string n)
{
    int sni = int.Parse(sn) - 1;
    _allStudentsArray[sni] = new Student();
    _allStudentsArray[sni].studentNumber = int.Parse(sn);
    _allStudentsArray[sni].topics = tp;
    _allStudentsArray[sni].testWeek = tw;
    _allStudentsArray[sni].gradeContent = int.Parse(gc);
    _allStudentsArray[sni].gradePrn = int.Parse(gp);
    _allStudentsArray[sni].gradeGrammar = int.Parse(gg);
    _allStudentsArray[sni].total = int.Parse(t);
    _allStudentsArray[sni].notes = n;
}

在名称空间的开头我有：

public class Student
{
    public int studentNumber;
    public string topics;
    public string testWeek;
    public int gradeContent;
    public int gradeGrammar;
    public int gradePrn;
    public int total;
    public string notes;
    public int studentsInClass;
    public int lastTestWeek;
}

Student[] _allStudentsArray;

但是一旦我尝试分配_allStudentArray[sni].studentNumber = sn，我就会收到一个null异常错误。我已经阅读了关于null异常的非常详细的答案，我认为它来自数组未正确初始化。但是连续两天我都无法找出原因。

这个NullReferenceException来自哪里？

0 个答案: