Converted test code generates an error (C# to VB.Net) - vb.net

Question

I have converted a C# code to VB.net and have applied the small adjustments required.
But when I test the code, it generates an error at the point where these instructions are:
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
I am no expert in DirectShow and I need that code to continue learning. Please Could anyone give me their generous help?
I would appreciate any help. Thank you.
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports DirectX.Capture
Imports DShowNET
Public Class MyWebCam
Inherits Form
' Muaz Khan (#muazkh) - http://muaz-khan.blogspot.com
Private capture As Capture = Nothing
Private filters As Filters = Nothing
Private counter As Integer = 1
Private timer As New Timer()
Private deviceNumber As Integer = 0
Public Sub New()
InitializeComponent()
End Sub
'============================================================================
Private Sub Form1_Shown(sender As Object, e As EventArgs)
filters = New Filters()
If filters.VideoInputDevices IsNot Nothing Then
Try
preview(deviceNumber)
Catch ex As Exception
MessageBox.Show("Maybe any other software is already using your WebCam." & vbLf & vbLf & " Error Message: " & vbLf & vbLf & ex.Message)
End Try
Else
btnStartVideoCapture.Enabled = False
MessageBox.Show("No video device connected to your PC!")
End If
timer.Interval = 600000
' 10 minutes!
AddHandler timer.Tick, Function(obj, evt)
If btnStartVideoCapture.Text = "STOP" Then
counter += 1
If capture IsNot Nothing AndAlso counter > 1 Then
capture.[Stop]()
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
capture.Start()
End If
End If
End Function
If filters.VideoInputDevices IsNot Nothing Then
For i = 0 To filters.VideoInputDevices.Count - 1
Dim device = filters.VideoInputDevices(i)
Dim btn = New Button()
btn.Text = i.ToString()
btn.ForeColor = Color.White
btn.BackColor = Color.DarkSlateBlue
btn.Width = 25
AddHandler btn.Click, Function(obj, evt)
Dim thisButton = DirectCast(obj, Button)
If Integer.Parse(thisButton.Text) <> deviceNumber Then
If capture IsNot Nothing Then
capture.Dispose()
capture.[Stop]()
capture.PreviewWindow = Nothing
End If
deviceNumber = Integer.Parse(thisButton.Text)
preview(deviceNumber)
End If
End Function
FlowLayoutPanel1.Controls.Add(btn)
Next
End If
End Sub
'============================================================================
Private Sub preview(deviceNo As Integer)
Try
' MessageBox.Show("deviceNo = > " + deviceNo);
capture = New Capture(filters.VideoInputDevices(deviceNo), filters.AudioInputDevices(0))
capture.PreviewWindow = Panel1
If btnStartVideoCapture.Text = "STOP" Then
counter += 1
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
End If
capture.Start()
Catch
End Try
End Sub
'============================================================================
Private Sub btnStartVideoCapture_Click(sender As System.Object, e As System.EventArgs) Handles btnStartVideoCapture.Click
startOrStopCapturing(capture)
End Sub
'============================================================================
Private Sub startOrStopCapturing(capture As Capture)
btnStartVideoCapture.Visible = False
'**** THE ERROR BEGINS TO APPEAR HERE ************
'****
'****
If capture IsNot Nothing Then
capture.[Stop]()
End If
If timer.Enabled Then
timer.[Stop]()
End If
If btnStartVideoCapture.Text = "START" Then
btnStartVideoCapture.Text = "STOP"
btnStartVideoCapture.BackColor = Color.Maroon
Try
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
capture.Start()
timer.Start()
Catch ex As Exception
MessageBox.Show("Error Message: " & vbLf & vbLf & ex.Message)
End Try
Else
btnStartVideoCapture.Text = "START"
btnStartVideoCapture.BackColor = Color.DarkSlateBlue
End If
btnStartVideoCapture.Visible = True
End Sub
'============================================================================
Private Sub InitializeComponent()
Me.btnStartVideoCapture = New System.Windows.Forms.Button()
Me.FlowLayoutPanel1 = New System.Windows.Forms.FlowLayoutPanel()
Me.Panel1 = New System.Windows.Forms.Panel()
Me.SuspendLayout()
'
'btnStartVideoCapture
'
Me.btnStartVideoCapture.BackColor = System.Drawing.Color.DarkSlateBlue
Me.btnStartVideoCapture.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.btnStartVideoCapture.ForeColor = System.Drawing.Color.White
Me.btnStartVideoCapture.Location = New System.Drawing.Point(498, 421)
Me.btnStartVideoCapture.Name = "btnStartVideoCapture"
Me.btnStartVideoCapture.Size = New System.Drawing.Size(89, 38)
Me.btnStartVideoCapture.TabIndex = 2
Me.btnStartVideoCapture.Text = "START"
Me.btnStartVideoCapture.UseVisualStyleBackColor = False
'
'FlowLayoutPanel1
'
Me.FlowLayoutPanel1.Location = New System.Drawing.Point(0, 421)
Me.FlowLayoutPanel1.Name = "FlowLayoutPanel1"
Me.FlowLayoutPanel1.Size = New System.Drawing.Size(502, 38)
Me.FlowLayoutPanel1.TabIndex = 3
'
'Panel1
'
Me.Panel1.Location = New System.Drawing.Point(0, -3)
Me.Panel1.Name = "Panel1"
Me.Panel1.Size = New System.Drawing.Size(587, 418)
Me.Panel1.TabIndex = 4
'
'Form1
'
Me.BackColor = System.Drawing.Color.Black
Me.ClientSize = New System.Drawing.Size(585, 458)
Me.Controls.Add(Me.Panel1)
Me.Controls.Add(Me.FlowLayoutPanel1)
Me.Controls.Add(Me.btnStartVideoCapture)
Me.Name = "Form1"
Me.ResumeLayout(False)
End Sub
Private WithEvents btnStartVideoCapture As System.Windows.Forms.Button
Friend WithEvents FlowLayoutPanel1 As System.Windows.Forms.FlowLayoutPanel
Friend WithEvents Panel1 As System.Windows.Forms.Panel
End Class

Answer 1

In the startStopCapturing you dont't check if the capture IsNothing. The capture object is initialized when you enter the preview method at the form Shown event or at the timer event.
Everywhere you have code in place that checks the capture object for IsNothing and to avoid using it but, in startStopCapturing, you don't have this check to protect the code in the IF that change the button text.
Private Sub startOrStopCapturing(capture As Capture)
btnStartVideoCapture.Visible = False
If capture IsNot Nothing Then
capture.[Stop]()
capture.Dispose()
capture = Nothing
If timer.Enabled Then
timer.[Stop]()
End If
btnStartVideoCapture.Text = "START"
btnStartVideoCapture.BackColor = Color.DarkSlateBlue
Else
Try
capture = New Capture(filters.VideoInputDevices(deviceNumber), _
filters.AudioInputDevices(0))
capture.Filename = counter & ".wmv"
capture.Cue()
capture.Start()
timer.Start()
btnStartVideoCapture.Text = "STOP"
btnStartVideoCapture.BackColor = Color.Maroon
Catch ex As Exception
MessageBox.Show("Error Message: " & vbLf & vbLf & ex.Message)
End Try
End If
btnStartVideoCapture.Visible = True
End Sub
Also this code in the inline button_click event seems to be wrong
If capture IsNot Nothing Then
capture.Dispose()
capture.[Stop]()
capture.PreviewWindow = Nothing
End iF
Do not use a disposed object and set it to Nothing because without that you could fool again your code in belivieng that the capture object is valid
If capture IsNot Nothing Then
capture.[Stop]()
capture.PreviewWindow = Nothing
capture.Dispose()
capture = Nothing
End iF