ByRef 關鍵字

方法引數之前的 ByRef 關鍵字表示將以允許方法更改（分配新值）引數的變數的方式傳送引數。

Class SomeClass
    Public Property Member As Integer
End Class

Module Program
    Sub Main()
        Dim someInstance As New SomeClass With {.Member = 42}
    
        Foo (someInstance)
        ' here someInstance is not Nothing
        ' but someInstance.Member is -42

        Bar(someInstance)
        ' here someInstance is Nothing
    End Sub

    Sub Foo(ByVal arg As SomeClass)
        arg.Member = -arg.Member ' change argument content
        arg = Nothing ' change (re-assign) argument
    End Sub

    Sub Bar(ByRef param As Integer)
        arg.Member = -arg.Member ' change argument content
        arg = Nothing ' change (re-assign) argument
    End Sub
End Module