我是初次使用类和OOP。我创建了一个类，该类将在每次调用时创建一个新标签。这是我的代码：
Public lbl As New Label
Public txt As New TextBox
Public controls As List(Of Control)
Public Sub New()
'Add a label
lbl.Name = "Label" & 1
lbl.Text = "Student " & 1 & ":"
lbl.Size = New Size(65, 20)
lbl.Location = New Point(10, (10 * 22) + 5)
controls.Add(lbl)
End Sub
当我调用此类时，我收到此错误消息：
An unhandled exception of type 'System.NullReferenceException' occurred in Project.exe Additional information: Object reference not set to an instance of an object.
消息突出显示的代码行是：
controls.Add(lbl)
任何帮助，将不胜感激，谢谢。
Public lbl As New Label
Public txt As New TextBox
Public controls As List(Of Control)
Public Sub New()
'Add a label
lbl.Name = "Label" & 1
lbl.Text = "Student " & 1 & ":"
lbl.Size = New Size(65, 20)
lbl.Location = New Point(10, (10 * 22) + 5)
If (controls is nothing) = True Then controls = new list(of Control)
controls.Add(lbl)
End Sub
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