Visual Basic - “对象引用未设置为对象的实例”

Question

我运行我的代码，我在try-catch的消息框中收到错误。错误是＆＃34;对象引用未设置为对象的实例＆＃34;请帮助我完全陷入困境，直到这个问题得到解决！

Public Class Development

    Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Try
            Call Deck.CreateUnmixedDeckIdList()
        Catch ex As Exception
            MsgBox("Failed" & vbCrLf & ex.Message)
        End Try
        For Each x As Integer In Deck.UnMixedIDDeck
            ListBox1.Items.Add(x & vbCrLf)
            ListBox1.Items.Add(x)
        Next
    End Sub
        Private Sub ShowMixedDeckIds(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            Deck.SuffleDeck()
            For Each x As String In Deck.MixedIDDeck
                ListBox1.Items.Add(x & vbCrLf)
            Next
        End Sub
End Class


Public Class Deck

    Public Shared UnMixedIDDeck, MixedIDDeck As List(Of Integer)

    Public Shared Sub CreateUnmixedDeckIdList()
        For i As Integer = 1 To 52
            UnMixedIDDeck.Add(i)
            Development.ListBox1.Items.Add(i)
        Next
    End Sub

    'SuffleDeck
    Public Shared Sub SuffleDeck()
        MixedIDDeck = RandomIDOrder(UnMixedIDDeck)
    End Sub '

    'Returns a list of numbers from the lenth of the given list
    Private Shared Function RandomIDOrder(ByVal List As List(Of Integer)) As List(Of Integer)
        Dim RandomList As New List(Of Integer)
        Dim R As New Random
        'Runs untill RandomList has the same lenth as GIVEN list
        Do While Not RandomList.Count = List.Count
            Dim S As String = List(R.Next(0, List.Count))
            'Checks to make sure value is not in list all ready. If it happen to be in the list it will not add it again and go back to lst While loop!
            If Not RandomList.Contains(S) Then
                RandomList.Add(S)
            End If
        Loop
        'Returns the new list of non repeating integers depending on the list you gave.
        Return RandomList
    End Function

End Class

Public Class Card

Public Function GetCardTitle(Id As Integer)
    Dim CardName As String
    CardName = ""
    Return CardName
End Function

End Class