В VB.NET вы можете отобразить окно сообщения с кнопками «Да», «Нет» и «Отмена», используя класс MessageBox. Вот несколько методов, которые вы можете использовать:

1. Использование метода MessageBox.Show:

   Dim result As DialogResult = MessageBox.Show("Message", "Title", MessageBoxButtons.YesNoCancel)
   If result = DialogResult.Yes Then
   ' Yes button clicked
   ' Perform corresponding action
   ElseIf result = DialogResult.No Then
   ' No button clicked
   ' Perform corresponding action
   ElseIf result = DialogResult.Cancel Then
   ' Cancel button clicked
   ' Perform corresponding action
   End If

2. Использование перечисления MessageBoxButtons:

   Dim result As DialogResult = MessageBox.Show("Message", "Title", MessageBoxButtons.YesNoCancel)
   Select Case result
   Case DialogResult.Yes
       ' Yes button clicked
       ' Perform corresponding action
   Case DialogResult.No
       ' No button clicked
       ' Perform corresponding action
   Case DialogResult.Cancel
       ' Cancel button clicked
       ' Perform corresponding action
   End Select

3. Обработка нажатий кнопок с помощью обработчиков событий:

   Private Sub ShowMessageBox()
   Dim messageBox As New MessageBox()
   AddHandler messageBox.YesButtonClicked, AddressOf YesButton_Clicked
   AddHandler messageBox.NoButtonClicked, AddressOf NoButton_Clicked
   AddHandler messageBox.CancelButtonClicked, AddressOf CancelButton_Clicked
   messageBox.Show("Message", "Title")
   End Sub
   Private Sub YesButton_Clicked(sender As Object, e As EventArgs)
   ' Yes button clicked
   ' Perform corresponding action
   End Sub
   Private Sub NoButton_Clicked(sender As Object, e As EventArgs)
   ' No button clicked
   ' Perform corresponding action
   End Sub
   Private Sub CancelButton_Clicked(sender As Object, e As EventArgs)
   ' Cancel button clicked
   ' Perform corresponding action
   End Sub