VB.NET中的参考资料

Question

对我来说有些不清楚的是VB.NET中的类的引用(指针？).我要问的问题可以通过一些测试来回答,但我想知道是否有人可以发布一个不错的解释(或链接).

如果您创建一个类:

Public Class ReferenceClass

    Private myBooleanValue As Boolean = False
    Public Property BooleanValue As Boolean
        Get
            Return myBooleanValue
        End Get
        Set(value As Boolean)
            myBooleanValue = value
        End Set
    End Property

End Class

然后是一个实际使用此类作为属性的类:

Public Class UsingClass

     Private myReference As ReferenceClass
     Public Property Reference As ReferenceClass
        Get
             return myReference
         End Get
         Set(value As ReferenceClass)
             myReference = value
         End Set
     End Property

     Public Sub New(ByVal Reference As ReferenceClass)
         myReference = Reference
     End Sub

End Class

然后像这样使用它:

Public Class RuntimeOrSomething

     Public Shared myReference As ReferenceClass
     Public Shared ReadOnly Property Reference As ReferenceClass
         Get
             If myReference Is Nothing Then myReference = new ReferenceClass()
             return myReference
         End Get
     End Property

     Public Shared Function BooleanCheck() As Boolean
         Reference.BooleanValue = True
         Dim tempClass As New UsingClass(Reference)
         tempClass.Reference.BooleanValue = False

         Return (tempClass.Reference.BooleanValue = Reference.BooleanValue)
     End Sub

     Public Shared Sub DoNothing()
          Reference.BooleanValue = True
          Dim someBoolean As Boolean = BooleanCheck

          ' Now Reference.Booleanvalue is "False"
     End Sub

End Class

现在函数BooleanCheck将始终返回true,即使引用是按UsingClass"值" 传递给新类,而不是通过引用传递给新类.所以类的副本是不言,但局部变量myReference中UsingClass还引用/指向特性Reference中RuntimeOrSomething.

如何优雅地解释这个？

Answer 1

引用指向对象的实例,它不是对象的实例.复制到对象的方向不会创建另一个对象,它会创建另一个也指向同一对象的引用.

Answer 2

我现在不能花很多时间在这个答案上 - 在我膝盖上蹒跚学步的火车上打字 - 但我有几篇文章可能有所帮助.它们是关于C#的,但同样适用于VB.NET:

• 引用类型和值类型
• 参数在.NET中传递