在 C# 中显示列表或数组中的项目

Question

我在尝试显示数组中的项目/对象列表时遇到了麻烦。

我正在做的是将学生的姓名、姓氏、年龄和科目（属性）标记添加到数组中。如果我以这种方式将 4 个学生添加到列表中，我想在单击“显示”按钮时再次在 RichTextBox 中显示所有学生及其属性。

如何在“displayAll_Click”功能中进行？我必须使用某种for循环吗？任何帮助将不胜感激。

我有以下代码：

在这个函数中，我将学生添加到数组中：

private void btnAdd_Click(object sender, EventArgs e)
    {
        // Create new student and assign name etc provided by user
        Student _Student = new Student();
        _Student.Name = txtName.Text;
        _Student.Surname = txtSurname.Text;
        _Student.Age = Convert.ToInt32(txtAge.Text);
        _Student.ITMark = Convert.ToInt32(txtIT.Text);
        _Student.MathMark = Convert.ToInt32(txtMath.Text);
        _Student.EngMark = Convert.ToInt32(txtEng.Text);

        MessageBox.Show("Student added.");

        // Increase counter and display how many students added so far
        CountStudents++;

        Average = Convert.ToInt32(txtIT.Text) + Convert.ToInt32(txtMath.Text) + Convert.ToInt32(txtEng.Text);
        _Student.AverageMark = Average / 3;

        //Display Student's properties in the richBox
        richTextBox1.Text = ("Student: " + Convert.ToString(CountStudents) +
                             "\nName: " + _Student.Name +
                            "\nSurname: " + _Student.Surname +
                             "\nAge: " + _Student.Age +
                             "\nStudent Average: " + Convert.ToString(_Student.AverageMark));

        //Add the newly added student to the ClassList array
        ClassList[CountStudents - 1] = _Student;

        //Clear the list after student is added
        txtAge.Clear();
        txtName.Clear();
        txtSurname.Clear();
        txtIT.Value = 0;
        txtMath.Value = 0;
        txtEng.Value = 0;
        txtName.Focus();
    }

在这个函数中，我想显示所有添加的学生，但是如何添加？

private void displayAll_Click(object sender, EventArgs e)
    {
        List<Student> _StudentList = new List<Student>();

        Student _Student = new Student();
        _Student.Name = txtName.Text;
        _Student.Surname = txtSurname.Text;
        _Student1.Age = Convert.ToInt32(txtAge.Text);
        _Student.ITMark = Convert.ToInt32(txtIT.Text);
        _Student.MathMark = Convert.ToInt32(txtMath.Text);
        _Student.EngMark = Convert.ToInt32(txtEng.Text);

        for (int i = 0; i < _StudentList; i++)
        {
            richTextBox1.Text = ("Student: " + Convert.ToString(CountStudents) +
                             "\nName: " + _Student.Name +
                            "\nSurname: " + _Student.Surname +
                             "\nAge: " + _Student.Age +
                             "\nStudent Average: " + Convert.ToString(_Student.AverageMark));
            i++;
        }
        //Displaying all the students
        MessageBox.Show("Display all students.");
    }

Answer 1

您每次都在为 Richtextbox 分配新文本：

使用

richTextBox1.Text +=

而不仅仅是

richTextBox1.Text =

完整代码：

for (int i = 0; i < _StudentList; i++)
{
    Student currentStudent = ClassList[i];    //get student from array
    richTextBox1.Text += ("Student: " + Convert.ToString(CountStudents) +
                         "\nName: " + currentStudent .Name +
                         "\nSurname: " + currentStudent .Surname +
                         "\nAge: " + currentStudent .Age +
                         "\nStudent Average: " + Convert.ToString(currentStudent .AverageMark));
            i++;    //you don't need to do it, let the loop handle it
}

它会将新字符串附加到其中而不删除之前的字符串。

Answer 2

尝试类似：

foreach(var student in _StudentList)
{
   richTextBox1.Text += ...
}

Answer 3

您的第二个函数看起来像一个大的复制和粘贴错误。 您正在创建一个空的 _StudentList，然后您继续迭代（尽管您将 int 与您的 for 中的 List 进行比较）。那么您将显示您刚刚从表单数据创建的一个学生。

试试这个：

private void displayAll_Click(object sender, EventArgs e)
{
    richTextBox1.Clear();
    for (int i = 0; i < ClassList.Count; i++)
    {
        richTextBox1.Text += ("Student: " + Convert.ToString(i) +
                         "\nName: " + ClassList[i].Name +
                        "\nSurname: " + ClassList[i].Surname +
                         "\nAge: " + ClassList[i].Age +
                         "\nStudent Average: " + Convert.ToString(ClassList[i].AverageMark));
    }
    //Displaying all the students
    MessageBox.Show("Display all students.");
}

Answer 4

您每次运行都会覆盖您的文本框，以及其他几个错误。我会使用 StringBuilder 和 foreach 循环

 StringBuilder sb = new StringBuilder();
 foreach (var student in _StudentList)
 {
      sb.Append(Environment.NewLine + "Name: " + student.Name);
      sb.Append(Environment.NewLine + "Surname: " + student.Surname);
      sb.Append(Environment.NewLine + "Age: " + student.Age);
      sb.Append(Environment.NewLine + "Student Average: " + student.AverageMark);
      sb.Append(Environment.NewLine);
 }

 richTextBox1.Text = sb.ToString();

另外，您的第一行 "Student: " + Convert.ToString(CountStudents) 没有多大意义，CountStudents 是学生人数，而不是该特定学生的唯一标识符。