Adding controls dynamically at runtime causing problems

[stateofidleness]

Hey fellas,
So what I'm trying to do is build 16 forms dynamically at runtime (all will be identical). These 16 forms each will display a camera, which is using an ActiveX control made by a 3rd party. I am able to create the forms correctly and provide all necessary parameters for each control, but since I have to declare my own AddHandler event which checks if the camera connected, I need to somehow reference the ActiveX control at runtime, but I can't tell it which form it's on because it says it's not declared.

Here is the code I'm using, Line 83 is where error occurs (in the Status Event)

Option Strict On
Public Class MainForm
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Setup the layout of all 16 cameras at run time
        Me.Width = Screen.PrimaryScreen.WorkingArea.Width
        BeginCameraLayout()
    End Sub
 
    Private Sub BeginCameraLayout()
        Dim screens As Integer
        Dim count As Integer = 1
        Dim camWidth As Integer = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)
 
        For screens = 1 To 16
            'This adds the necessary controls to the camera forms
            Dim liveStatusLabel As New Label
            Dim f As New Form
            f.Controls.Add(liveStatusLabel)
            'Format the new form's properties before displaying
            f.Width = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)
            f.Height = CInt((Screen.PrimaryScreen.WorkingArea.Height - Me.Height) / 4)
            f.ShowInTaskbar = False
            f.ShowIcon = False
            f.ControlBox = False
            f.Text = "Camera " & screens
            f.MinimizeBox = False
            f.Show()
            f.Controls.Add(AddVideoScreen(screens)) 'Call to create the ActiveX control
            Select Case screens
                Case 1, 2, 3
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 4
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 5, 6, 7
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 8
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 9, 10, 11
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 12
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 13, 14, 15
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 16
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
            End Select
        Next
    End Sub
 
    Private Function AddVideoScreen(ByVal screen As Integer) As AxVIDEOCONTROLLib.AxVideoControl
        Dim vcLive As New AxVIDEOCONTROLLib.AxVideoControl
        vcLive.Dock = DockStyle.Fill
        vcLive.DLLPath = Application.StartupPath & "\TL4516UL.dll"
        vcLive.UserName = "live"
        vcLive.Password = "live"
        vcLive.IPAddress = "100.100.100.100"
        vcLive.Port = 53705
        vcLive.CameraID = screen
        vcLive.Connect()
        AddHandler vcLive.Status, New AxVIDEOCONTROLLib._DVideoControlEvents_StatusEventHandler(AddressOf vcLive_Status)
        Return vcLive
    End Function
 
    Private Sub vcLive_Status(ByVal sender As Object, ByVal e As AxVIDEOCONTROLLib._DVideoControlEvents_StatusEvent)
        If ((e.strMessage = "Status:Connection Established") OrElse e.strMessage.Contains("Error")) Then
            If (e.strMessage = "Status:Connection Established") Then
               f.vcLive.PlayLive() 'This line throws error. 'f' is not declared          
            End If
        End If
    End Sub
 
End Class

Also, if I comment out the error line, just to test, I get this error:

A first chance exception of type 'System.Windows.Forms.AxHost.InvalidActiveXStateException' occurred in AxInterop.VIDEOCONTROLLib.dll

on the line referencing the .dll path. I am thinking it may be because after the first iteration, the .dll is in use and therefore future iterations can't use it, causing the error. I'm trying to take a very OOP approach to this project (keeping things in their own subs and whatnot) but the referencing and scope is throwing me off quite a bit.

[techgnome]

Why not create a form at design time with everything all hooked up, then at run time, simply create new instances of the form?

then you could skip the call to f.Controls.Add(AddVideoScreen(screens))
And your status event would be contained in the form, then you could simply use Me. to get to the form instance as needed.

-tg

[NickThissen]

Of course it doesn't know f, you haven't declared it. You've only declared a variable named f in the BeginCameraLayout method, which is a local variable and thus does not exist in any other method.

First of all, I think your AddHandler line is a bit strange. It seems you are creating an event delegate manually, which you shouldn't have to. Doesn't this work:

AddHandler vcLive.Status, AddressOf vcLive_Status

I'm not sure if it makes a difference, but it might.

Anyway, if that works, the 'sender' parameter in the vcLive_Status method should be the AxVideoControl object that raised the event. So, you can simply cast it, and use its methods:

Dim vcLive = DirectCast(sender, AxVIDEOCONTROLLib.AxVideoControl)
vcLive.PlayLive()

About the other error, I'm hoping it doesn't occur after you use this code, because I've no idea what could cause that.


EDIT
While my solution should work, and explains what is going wrong, techgnome's solution is better. Just put the control on a form during design-time and handle its event on that form.

EDIT2
But, you may get into 'trouble' with the CameraID integer. Instead of passing it when creating the camera control (which you now do during design-time probably, or still in code but only once), you can make your form accept the ID as an argument in its contstructor, or as a public property (or both).

Public Class CameraForm
   Inherits Form
  
   Public Sub New(ByVal cameraId As Integer)
      Me.InitializeComponent()   'this is always required
      
      vcLive.CameraID = cameraId   'vcLive is the name of the camera control on the form
 
      'set other properties here, such as size and position
   End Sub
 
   '...
End Class

Now, you just pass the id when you create the form:

For screen As Integer = 1 To 16
   Dim f As New CameraForm(screen)  'pass it here
   'you don't need to set 38 gazillion properties here, you can set them in the forms constructor instead
   'of course you still CAN set the properties here, it's just not as 'elegant' :)
   f.Show()
Next

[stateofidleness]

ahh much appreciated guys.
I actually started out with a "template" form to use for all 16 cameras, but then wasn't sure if I'd need to create 16 of these forms or what.

As I may have different views (4 cameras 2x2, 16 cameras 4x4 etc), I would just set up my For loop accordingly? The properties of the form will change if I do this though which is why I can't declare them on the Form in design time. The .Top, .Left, .Width and .Height properties will all change depending on how many are showing.

How can I still dynamically create these forms (based off the form in Designer View) and still dynamically set their properties?

[NickThissen]

You can set the properties that are always fixed (ShowInTaskbar, ShowIcon, ControlBox, etc, just a few I could see quickly) during design-time, or in the forms constructor or Form_Load event. You can then, after declaring a new form or after calling its Show method, set the other properties like you are doing now. It doesn't really matter though, you could also set all the properties like you are doing now. It just seems more appropriate to have most of these properties (well, as much as possible) in the form class itself so you don't clutter up your form creation code with stuff you can set elsewhere.

[techgnome]

Same as you are now:

    Private Sub BeginCameraLayout()
        Dim screens As Integer
        Dim count As Integer = 1
        Dim camWidth As Integer = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)

        For screens = 1 To 16
            Dim f As New cameraTemplateForm
            'Format the new form's properties before displaying
            f.Width = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)
            f.Height = CInt((Screen.PrimaryScreen.WorkingArea.Height - Me.Height) / 4)
            f.Text = "Camera " & screens

            'Set these at Design time in the template form
            'f.ShowInTaskbar = False
            'f.ShowIcon = False
            'f.ControlBox = False
            'f.MinimizeBox = False

            f.Show()

            Select Case screens
                Case 1, 2, 3
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 4
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 5, 6, 7
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 8
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 9, 10, 11
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 12
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 13, 14, 15
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 16
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
            End Select
        Next
    End Sub

easy as that...

-tg

[stateofidleness]

ah very cool, here's what i got:

In my MainForm:

Option Strict On
Public Class MainForm
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Width = Screen.PrimaryScreen.WorkingArea.Width
        'Setup the layout of all 16 cameras at run time
        BeginCameraLayout()
    End Sub
 
    Private Sub BeginCameraLayout()
        Dim screens As Integer
        Dim count As Integer = 1
        Dim camWidth As Integer = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)
 
        For screens = 1 To 16
            'Add Camera Forms and lay them out correctly
            Dim f As New CameraForm
            f.Width = CInt(Screen.PrimaryScreen.WorkingArea.Width / 4)
            f.Height = CInt((Screen.PrimaryScreen.WorkingArea.Height - Me.Height) / 4)
            f.Show()
            Select Case screens
                Case 1, 2, 3
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 4
                    f.Top = Me.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 5, 6, 7
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 8
                    f.Top = Me.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 9, 10, 11
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 12
                    f.Top = Me.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count = 1
                Case 13, 14, 15
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
                    count += 1
                Case 16
                    f.Top = Me.Height + f.Height + f.Height + f.Height
                    f.Left = (camWidth * count) - camWidth
            End Select
        Next
    End Sub
 
End Class

In my CameraForm:

Public Class CameraForm
    Private Sub CameraForm_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        camera.DLLPath = Application.StartupPath & "\TL4516UL.dll"
        camera.Connect()
        'AddHandler camera.Status, AddressOf camera_Status
        AddHandler camera.Status, New AxVIDEOCONTROLLib._DVideoControlEvents_StatusEventHandler(AddressOf camera_Status)
    End Sub
 
    Private Sub camera_Status(ByVal sender As Object, ByVal e As AxVIDEOCONTROLLib._DVideoControlEvents_StatusEvent)
        MsgBox(e.ToString & " " & e.strMessage)
        If ((e.ToString = "Status:Connection Established") OrElse e.ToString.Contains("Error")) Then
            If (e.ToString = "Status:Connection Established") Then
                Dim cam As New AxVIDEOCONTROLLib.AxVideoControl
                cam = DirectCast(sender, AxVIDEOCONTROLLib.AxVideoControl)
                cam.PlayLive()
            End If
        End If
    End Sub
End Class

Here is the product:



For some reason the AddHandler event isn't firing. I've tried both declarations and neither one will make it fire.

[techgnome]

don't use the AddHandler.... plop the control right onto the form then double click it, and set the event handler code just like any other control you are using... the reason to use add handler is if you want to dynamically link code to a controls (or a lot of controls to one event handler)... this is one case where it may not be working right for some reason.

-tg

[NickThissen]

It seems you are not setting a whole load of properties on the AxVideoPlayer control that you were setting before (CameraID, Username, Password, IPAddress, etc). Not sure if that is related.

Anyway, you don't need to use AddHandler when you added your control during design-time. Just handle its Status event as you would handle a button's Click event. That said, AddHandler should work just fine too, so that can't cause your problem.

[stateofidleness]

as I have no documentation with the correct usage of the .dll, I'm kinda shooting in the dark. Removing the Addhandler and doing it through design-view worked a charm. The event is now firing as expected.
The problem I'm having is I don't think I am supposed to create a new connection for each camera with separate logins etc..

I think I am supposed to connect using:

camera.DLLPath = Application.StartupPath & "\TL4516UL.dll"
camera.IPAddress = "100.100.100.100"
camera.Port = 53705
camera.UserName = "admin"
camera.Password = "admin"

I think I need to set all that and then connect, and while connected get a different cameraID for each ActiveX control.. I'm just not sure how to do that

Pseudo of what I think should be done

Set properties for the connection
Connect
Load 16 Form instances
Load a different CameraID for each form