Is there an idiomatic .net way to implement "training card help"?

Question

We have a VB6 app that has implemented a handler for WM_TCARD messages from an HTML Help file. It navigates within the application and opens the relevant screens etc.

How does one do this in a WinForms app?

The only way I can immediately see is to handle the window procedure and process the WM_TCARD message in exactly the same way we were doing for the VB6 app.

Is there a more .net way to do this?

Answer 1

You'll have to handle the messages yourself. However, it's pretty easy to make a class which does this for you. E.g.:

public class HelpCards : IMessageFilter {
    const int WM_TCARD = 0x52;
    const int ID_NOTIFICATION = 4242;

    public enum TCardAction: int {
        IDOK = 1,
        IDCANCEL = 2,
        IDABORT = 3,
        IDRETRY = 4,
        IDIGNORE = 5,
        IDYES = 6,
        IDNO = 7,
        IDCLOSE = 8,
        IDHELP = 9,

        HELP_TCARD = 0x8000,
        HELP_TCARD_DATA = 0x0010,
        HELP_TCARD_OTHER_CALLER = 0x0011,
        HELP_TCARD_OTHER_NEXT = 0x0011,
    }

    public HelpCards() {
        Application.AddMessageFilter(this);
    }

    public delegate void OKReceived();
    public event OKReceived OnOKReceived; 

    public bool PreFilterMessage(ref Message m) {
        if (m.Msg == WM_TCARD && (int)m.WParam == ID_NOTIFICATION) {
            switch ((TCardAction)m.LParam) {
                case TCardAction.IDOK:
                    if (OnOKReceived != null) {
                        OnOKReceived();
                    }
                    break;
                    // etc.
            }

            return true; // true means message was handled
        }

        return false;
    }
}

Then, in the place where you want to subscribe (probably in your form somewhere) use

hc = new HelpCards();
hc.OnOKReceived += new OKReceived(hc_OnOKReceived);

And have hc defined in the class definition of the form. Like so

HelpCards hc;

And somewhere have the handling function:

void hc_OnOKReceived() {
    throw new NotImplementedException();
}

Obviously you will need to do the rest yourself. But that should get you started.