Question

I have a a wait form FormWait (long running task notification), that has ShowMessage(string message) function.

Often happens in code:

public RootCall() 
{
   FormWait.ShowMessage("Begin long task 1..."); 

   ChildCall();

   FormWait.CloseForm();   
}

public ChildCall() 
{
   FormWait.ShowMessage("Begin long task 2..."); 

   // some code here

   FormWait.CloseForm();   
}

FormWait on root shows the message to the user, but before closing it on root level, there is another ShowMessage of child and CloseForm of child.

I have a couple of solutions to resolve this:

1. Like in code provided the methods are static and operate on one static System.Windows.Forms.Form instance. On every ShowMessage there is a static variable that increments and on every CloseForm it decrements. So by looking on that variable I can understand if I really need to close the form (if I’m or not on root level), or its just a nested CloseForm call. And on every ShowMessage new string just updated on already visible form.

2. For every new ShowMessage call create new instance of the form, but this is really wired to see. So almost sure I will not pick this solution.

Any ideas, how can I manage WaitForm (form that signals to user about long running tasks) in case of nested calls, by making also the developer life easier.?

Answer 1

The Stack<> class is the natural fit for this:

public partial class WaitForm : Form {
    private WaitForm() {
        InitializeComponent();
    }
    private static WaitForm instance;
    private static Stack<string> messages = new Stack<string>();

    public static void ShowMessage(string message) {
        if (instance == null) {
            instance = new WaitForm();
            instance.FormClosed += delegate { instance = null; };
            instance.Show();
        }
        messages.Push(message);
        instance.lblMessage.Text = message;
        instance.Update();
    }

    public static void CloseForm() {
        messages.Pop();
        if (instance != null) {
            if (messages.Count == 0) instance.Close();
            else instance.lblMessage.Text = messages.Peek();
        }
    }
}

Don’t forget to put the CloseForm() call in a finally block so this is all exception safe.