我只是在通过课程的方式工作，在vb.net上做一个项目，有些事情我想不通。
在我的代码中，我有这个类（你不需要阅读它，它只是将文件从路径A复制到B）：

Public Class FileCopyExample
    Public Sub New()
        Dim progressForm As New ProgressForm()
        progressForm.Show()
    End Sub
    Public Async Function CopyFolderContentsAsync(sourceFolder As String, destinationFolder As String) As Task
        
        If Not Directory.Exists(sourceFolder) Then
            Throw New DirectoryNotFoundException($"Source folder '{sourceFolder}' not found.")
        End If
        If Not Directory.Exists(destinationFolder) Then
            Directory.CreateDirectory(destinationFolder)
        End If
        Dim files = Directory.GetFiles(sourceFolder)
        Dim tasks As New List(Of Task)()
        For Each file In files
            Dim fileName = Path.GetFileName(file)
            Dim destinationFilePath = Path.Combine(destinationFolder, fileName)
            tasks.Add(CopyFileAsync(file, destinationFilePath))
        Next
        Dim subFolders = Directory.GetDirectories(sourceFolder)
        For Each subFolder In subFolders
            Dim folderName = Path.GetFileName(subFolder)
            Dim destinationSubFolder = Path.Combine(destinationFolder, folderName)
            tasks.Add(CopyFolderContentsAsync(subFolder, destinationSubFolder))
        Next
        Await Task.WhenAll(tasks)
    End Function
    Private Async Function CopyFileAsync(sourcePath As String, destinationPath As String) As Task
        Using sourceStream As FileStream = File.OpenRead(sourcePath)
            Using destinationStream As FileStream = File.Create(destinationPath)
                Await sourceStream.CopyToAsync(destinationStream)
            End Using
        End Using
    End Function
End Class

我想做的是打开一个带有一个小ProgressBar对象的表单，以显示文件传输过程的进展。
所以我创建了另一个类，它打开一个表单并在上面添加一个进度条。

Public Class ProgressForm
    Inherits Form
    Public progressBar As New ProgressBar()
    Public startButton As New Button()
    Public Sub New()
        InitializeComponents()
    End Sub
    Private Sub InitializeComponents()
        Me.Text = "Progress Form"
        Me.Size = New Size(300, 150)
        progressBar.Minimum = 0
        progressBar.Maximum = 100
        progressBar.Value = 0
        Me.Controls.Add(progressBar)
        Me.Controls.Add(startButton)
    End Sub
End Class

现在，如果我想ProgressBar工作，我将需要引用对象ProgressBar（内）我的其他类（FileCopyExample），但如果我尝试这样做，我收到错误
错误BC30469对非共享成员的引用需要对象引用。
我试图将ProgressBar声明为public，但它不起作用。谁能告诉我问题出在哪里？