Question

My scenario:

Windows Forms Application with a base master (mdi) form.

An Interface that has an event:

Public Interface IDoSomething  Event AddFilter() 

Modal popup window implements the interface and decalres event:

Public Class frmPopup Implements IDoSomething  Public Event AddFilter() Implements IDoSomething.AddFilter 

Popup also contains code to fire the event:

RaiseEvent AddFilter() 

Base master form contains code that discovers and launches popup forms that implement a specified interface.

A form in the application launches the popup (that implements the interface) and handle any events that it fires. So I have the following code in the form:

Public Class frmMyForm  Public WithEvents m_Popup As IDoSomething  Public Sub m_Popup_AddFilter() Handles m_Popup.AddFilter      MsgBox('I'm in')  End Sub 

The code is all working, up until the stage where the event is fired. The popup loads without any issues but when the event fires it seems to drop off the face of the earth and is not being picked up by the main form – frmMyForm. I suspect it may have something to do with the way the popup form is being launched from the base master form via the discovery of the interface.

ADDITIONAL CODE – to expand on ‘Base master form contains code that discovers and launches popup forms that implement a specified interface’:

The idea of the popup forms that are being used is to return a business object to the form that opened it using events. The popup form Interface (IDoSomething) inherits another interface – IBusinessObjectSelector which specifies that the form will return a business object.

So the function in the base master form is:

Public Function GetBusinessObjectUsingPopup(Of O, F As IBusinessObjectSelector)                (ByRef dicPropertyValues As Dictionary(Of String, Object),                  Optional ByVal titleText As String = '')                  As O Implements IBaseMasterForm.GetBusinessObjectUsingPopup  Dim objBusinessObjectSelector As IBusinessObjectSelector = GetPopup(Of F)(False)            objBusinessObjectSelector.InitialiseForm()      ' Activate and show the dialog     If objBusinessObjectSelector.ShowPopup() <> Windows.Forms.DialogResult.OK Then         ' The user cancelled the load, so just exit         Return Nothing     End If      GetBusinessObjectUsingPopup = CType(objBusinessObjectSelector.SelectedBusinessObject, O)  End Function 

And Popup Code:

Public Function GetPopup(Of F As IBasePopupChildForm)             (Optional ByVal initialisePopupPriorToReturn As Boolean = True) As F               Implements IBaseMasterForm.GetPopup      Dim lstIBasePopupChildForm As List(Of F) = GetInterfaces(Of F)()             lstIBasePopupChildForm(0).MyIBaseMasterForm = Me     If initialisePopupPriorToReturn Then         lstIBasePopupChildForm(0).InitialiseForm()     End If     Return lstIBasePopupChildForm(0) End Function 

Note – GetInterfaces(Of F)() simply scans the assembly and returns a list of forms that implement the required interface. Some validation has been chopped out that returns messages if multiple forms that implement the interface are found.

Answer 1

The critical part is initializing m_Popup correctly. You haven’t said anything about that. Some sample code:

Form2:

Public Class Form2     Implements IDoSomething     Public Event AddFilter() Implements IDoSomething.AddFilter      Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click         RaiseEvent AddFilter()     End Sub End Class  Public Interface IDoSomething     Event AddFilter() End Interface 

Form1:

Public Class Form1     Private WithEvents mPopup As IDoSomething      Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load         Dim f2 As New Form2         f2.Show(Me)         mPopup = f2     End Sub      Private Sub mPopup_AddFilter() Handles mPopup.AddFilter         MsgBox('yada')     End Sub End Class 

The mPopup = f2 statement in this code is key.