Question

This is the form code and every time I test some inputs, the application will open and then immediately close and I can’t figure out what is causing it.

  namespace Assignment2
  {
public partial class IsmClassForm : Form
{
    public IsmClassForm()
    {

        InitializeComponent();
    }
    private void IsmClassForm_Load(object sender, EventArgs e)
    {
    }

    protected Student m_student;
    protected Course m_course;
    protected IsmClassForm m_next;
    protected EnrollmentForm m_home;

     public bool TestPrerequisites()

    {
        if (!m_student.Record.MeetsPrerequisites(m_course.Number))
        {
            MessageBox.Show("The registrar reports that you don't meet the prerequisites for " + m_course.Prefix + m_course.Number.ToString());
            m_student.PridePoints = m_student.PridePoints - 5;
            m_student.Record.Remove(m_course);
            return false;
        }
        return true;
    }
    public string Description
    {
        get
        {
            return textDescription.Text;
        }
        set
        {
            textDescription.Text = value;
        }
    }

    public string Title
    {
        get
        {
            return this.Text;
        }
        set
        {
            this.Text = value;
        }
    }
    public string Welcome
    {
        get
        {
            return labelWelcome.Text;
        }
        set
        {
            labelWelcome.Text = value;
        }
    }



    public bool Initialize(Student student, int course, IsmClassForm next, EnrollmentForm home)
    {
        if (student == null) return false;
        m_student = student;
        m_next = next;
        m_home = home;
        m_course = m_student.Record.FindEnrolled(course);
        if (m_course == null)
        {
            return false;
        }

        labelCourse.Text = m_course.Prefix + "-" + m_course.Number.ToString();
        return TestPrerequisites();

    }


    public enum DropMode
    {
        FreeDrop, PayDrop, Withdraw, NoDrop
    };
    DropMode mState = DropMode.FreeDrop;
    public DropMode Drop
    {
        get
        {
            return mState;
        }
        set
        {
            mState = value;
            UpdateDrop();
        }
    }

    public void UpdateDrop()
    {
        switch (Drop)
        {
            case DropMode.FreeDrop:
                buttonDrop.Text = "Drop";
                break;
            case DropMode.PayDrop:
                buttonDrop.Text = "Drop";
                break;
            case DropMode.Withdraw:
                buttonDrop.Text = "Withdraw";
                break;
            case DropMode.NoDrop:
                buttonDrop.Text = "Done";
                break;
        }

    }

    protected void buttonDrop_Click(object sender, EventArgs e)
    {
        switch (Drop)
        {
            case DropMode.FreeDrop:
                m_student.PridePoints = m_student.PridePoints - 5;
                m_student.Record.Remove(m_course);
                m_course = null;
                break;
            case DropMode.PayDrop:
                m_student.PridePoints = m_student.PridePoints - 10;
                m_student.WealthPoints = m_student.WealthPoints - 500;
                m_student.Record.Remove(m_course);
                m_course = null;
                break;
            case DropMode.Withdraw:
                m_student.PridePoints = m_student.PridePoints - 50;
                m_student.WealthPoints = m_student.WealthPoints - 500;
                m_course.Grade = "W";
                break;
            case DropMode.NoDrop:
                m_student.WealthPoints = m_student.WealthPoints - 500;
                break;
        }
        Close();


    }

    protected void IsmClassForm_FormClosed(object sender, FormClosedEventArgs e)
    {
        if (e.CloseReason == CloseReason.UserClosing)
        {
            //The student not having a grade suggest the buttons were ignored
            if (m_course != null && m_course.Grade == null)
            {
                m_course.Grade = "F";
                m_student.PridePoints = m_student.PridePoints - 100;
                m_student.WealthPoints = m_student.WealthPoints - 500;
            }
            if (m_next != null) m_next.Show();
            else if (m_home != null) m_home.Show();
        }






    }

And here are some test inputs:

 static void TestIsmClassForm()
    {
        Student tjt1 = new Student("Travis Todd");
        tjt1.Record = new Transcript();
        tjt1.Record.Add(new Course(1, 3113, "B", false));
        tjt1.Record.Add(new Course(1, 3232, "C", false));
        tjt1.Record.Add(new Course(2, 3113, "A", true));
        tjt1.Record.Add(new Course(2, 3232, null, true));
        tjt1.Record.Add(new Course(2, 4220, null, true));
        IsmClassForm f4220 = new IsmClassForm();
        IsmClassForm f3232 = new IsmClassForm();
        IsmClassForm f4212 = new IsmClassForm();
        f4212.Initialize(tjt1, 4212, f3232, null);
        f3232.Initialize(tjt1, 3232, f4220, null);
        f4220.Initialize(tjt1, 4220, null, null);
        f4212.Show();
    }

This does use some other classes in the project and their forms, but I the other functions all work and these is the only problem I have found so far. Am I missing something glaringly obvious?

Thank you,
Travis

Answer 1

You have two ways to achieve this;

Given your entry method:

public static void Main()     
{         
    TestIsmClassForm();    
} 

You can use Application.Run or Form.ShowDialog:

static void TestIsmClassForm()
{
    ...All of your original code...

    Application.Run(f4212.Show());

    //OR

    f4212.ShowDialog()

}

What is happening right now is that Form.Show is non-blocking – the application calls it, continues on out of the method, and closes.

Application.Run will show the form and wait until it closes before exiting the application. Form.ShowDialog() will block the calling method until the form is closed.

Application.Run is preferred because it guarantees the form used as the application host is marshalled in the “Main” or “GUI” thread. ShowDialog() makes no guarantee when run direct from Main()(Application.MessageLoop is false) and it is possible for some surprisingly annoying threading bugs to happen – so the majority of the time Application.Run is the best way to achieve what you are doing.