在 VB.net 中使用线程

Question

I'm having trouble using threading in a VB.net application I'm writing. I have a really simple version here to illustrate the problem I'm having.

It works perfectly if I load my form and have the VNC control connect to my VNC server as a single thread application using this code:

Imports VncSharp
Imports System.Windows.Forms
Imports System.ComponentModel
Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        If Not RemoteDesktop1.IsConnected Then
            Dim Host As String = "10.0.0.1"
            RemoteDesktop1.Connect(Host)
        End If
    End Sub
End Class

In order to make the connection occur in the background, this is the code I've tried using the backgroundworker control. I followed the information in this article to handle referencing the controls on the form using an instance, but I still get an error when it tries to use the VNCSharp control (RemoteDesktop1) to connect to a VNC server at the line: Instance.RemoteDesktop1.Connect(Host)

The error is:

System.InvalidOperationException: 'Cross-thread operation not valid: Control 'RemoteDesktop1' accessed from a thread other than the thread it was created on.'

Here's the code:

Imports VncSharp
Imports System.Windows.Forms
Imports System.ComponentModel
Public Class Form1
    
    'Taken from https://stackoverflow.com/questions/29422339/update-control-on-main-form-via-background-worker-with-method-in-another-class-v
    Private Shared _instance As Form1
    Public ReadOnly Property Instance As Form1
        Get
            Return _instance
        End Get
    End Property

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        _instance = Me
        BackgroundWorker1.RunWorkerAsync()
    End Sub

    Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        System.Threading.Thread.Sleep(1000)
        If Not Instance.RemoteDesktop1.IsConnected Then
            Dim Host As String = "10.0.0.1"
            Instance.RemoteDesktop1.Connect(Host)
            'Connect()
        End If
    End Sub

    Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
        MsgBox("BG1 complete")
    End Sub
End Class

Answer 1

I figured it out - one part of the code in the post I linked to on threading held the answer: I needed to use Invoke() to reference the form RemoteDesktop control:

Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
  System.Threading.Thread.Sleep(1000)
    If Not Instance.RemoteDesktop1.IsConnected Then
      Me.Instance.Invoke(Sub()
        Dim Host As String = "10.61.41.7"
        Me.RemoteDesktop1.Connect(Host)
      End Sub)
  End If
End Sub

instead of just putting Instance.RemoteDesktop1.Connect(Host)