Async Await Task.Run更新模式表单抛出异常

Question

我有两种形式 它运行正常，但如果我按模式窗体的取消按钮然后显示错误。 任何人都可以帮我解决问题吗？ 我的代码如下：

1）

Public Class FRMWait

    Public MinValue As Integer = 0
    Public MaxValue As Integer = 100

    Private Sub FRMWait_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        With Me
            .ProgressBa1.MinimumValue = .MinValue
            .ProgressBa1.MaximumValue = .MaxValue
        End With
    End Sub

    Public Sub UpdateBar(ByVal Progress As Integer)
        With Me
            .ProgressBarControlProgress.value = Progress
        End With
    End Sub
    Private Sub ButtonCancel_Click(sender As Object, e As EventArgs) Handles ButtonCancel.Click
        With Me
            .DialogResult = DialogResult.Cancel
        End With
    End Sub
End Class

2）

Imports System.Threading

Public Class FRMTest
    Private WaitForm As New FRMWait
    Private _CTS As CancellationTokenSource

    Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        'Control.CheckForIllegalCrossThreadCalls = False
    End Sub

    Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        With Me
            .WaitForm = New FRMWait
            ._CTS = New CancellationTokenSource()
            Try
                Await Task.Run(Sub() RunLongTask())
                .WaitForm.ShowDialog()
                If .WaitForm.DialogResult = DialogResult.Cancel Then
                    ._CTS.Cancel()
                End If
            Catch Exp As Exception
                MsgBox(Exp.Message)
            Finally
                If ._CTS IsNot Nothing Then ._CTS = Nothing
            End Try
        End With
    End Sub

    Private Async Sub RunLongTask()
        With Me
            .WaitForm.MinValue = 0
            .WaitForm.MaxValue = 100
            For i = 0 To 100
                If ._CTS.IsCancellationRequested Then
                    Await Task.Delay(1000)
                    Exit For
                End If
                .WaitForm.UpdateBar(i)
                Await Task.Delay(100)
            Next
            .WaitForm.Close()
        End With
    End Sub
End Class