برنامج علامات الطلاب

List<int> marks = new List<int>();

private void btnAdd_Click(object sender, EventArgs e)
{
    if (txtName.Text.Trim() == "") { MessageBox.Show("أدخل اسم الطالب"); return; }
    int mark;
    if (!int.TryParse(txtMark.Text, out mark) || mark < 0 || mark > 100)
    { MessageBox.Show("العلامة رقم بين 0 و 100"); return; }
    marks.Add(mark);
    lstStudents.Items.Add(txtName.Text.Trim() + " - " + mark);
    ShowAverage();
    txtName.Clear(); txtMark.Clear(); txtName.Focus();
}

private void ShowAverage()
{
    if (marks.Count == 0) { lblAvg.Text = "المعدل: -"; return; }
    lblAvg.Text = "المعدل: " + marks.Average().ToString("0.0");
}

private void btnDelete_Click(object sender, EventArgs e)
{
    int i = lstStudents.SelectedIndex;
    if (i == -1) { MessageBox.Show("اختر طالباً أولاً"); return; }
    lstStudents.Items.RemoveAt(i);
    marks.RemoveAt(i);
    ShowAverage();
}

private void btnSave_Click(object sender, EventArgs e)
{
    List<string> lines = new List<string>();
    foreach (object item in lstStudents.Items) lines.Add(item.ToString());
    File.WriteAllLines("students.txt", lines);
    MessageBox.Show("تم الحفظ");
}

private void Form1_Load(object sender, EventArgs e)
{
    if (!File.Exists("students.txt")) return;
    foreach (string line in File.ReadAllLines("students.txt"))
    {
        lstStudents.Items.Add(line);
        marks.Add(int.Parse(line.Substring(line.LastIndexOf(" - ") + 3)));
    }
    ShowAverage();
}