访问修饰符的示例

在以下示例中，考虑你有一个托管两个项目的解决方案： ConsoleApplication1 和 SampleClassLibrary 。第一个项目将包含 SampleClass1 和 SampleClass2 类。第二个将具有 SampleClass3 和 SampleClass4 。换句话说，我们有两个程序集，每个程序集有两个类。 ConsoleApplication1 引用了 SampleClassLibrary 。

了解 SampleClass1.MethodA 如何与其他类和方法交互。

SampleClass1.vb：

Imports SampleClassLibrary

Public Class SampleClass1
    Public Sub MethodA()
        'MethodA can call any of the following methods because
        'they all are in the same scope.
        MethodB()
        MethodC()
        MethodD()
        MethodE()

        'Sample2 is defined as friend. It is accessible within
        'the type itself and all namespaces and code within the same assembly.
        Dim class2 As New SampleClass2() 
        class2.MethodA()
        'class2.MethodB() 'SampleClass2.MethodB is not accessible because
                          'this method is private. SampleClass2.MethodB
                          'can only be called from SampleClass2.MethodA,
                          'SampleClass2.MethodC, SampleClass2.MethodD
                          'and SampleClass2.MethodE
        class2.MethodC()
        'class2.MethodD() 'SampleClass2.MethodD is not accessible because
                          'this method is protected. SampleClass2.MethodD
                          'can only be called from any class that inherits
                          'SampleClass2, SampleClass2.MethodA, SampleClass2.MethodC,
                          'SampleClass2.MethodD and SampleClass2.MethodE
        class2.MethodE()

        Dim class3 As New SampleClass3() 'SampleClass3 resides in other
                                         'assembly and is defined as public.
                                         'It is accessible anywhere.
        class3.MethodA()
        'class3.MethodB() 'SampleClass3.MethodB is not accessible because
                          'this method is private. SampleClass3.MethodB can
                          'only be called from SampleClass3.MethodA,
                          'SampleClass3.MethodC, SampleClass3.MethodD
                          'and SampleClass3.MethodE

        'class3.MethodC() 'SampleClass3.MethodC is not accessible because
                          'this method is friend and resides in another assembly.
                          'SampleClass3.MethodC can only be called anywhere from the
                          'same assembly, SampleClass3.MethodA, SampleClass3.MethodB,
                          'SampleClass3.MethodD and SampleClass3.MethodE

        'class4.MethodD() 'SampleClass3.MethodE is not accessible because
                          'this method is protected friend. SampleClass3.MethodD
                          'can only be called from any class that resides inside
                          'the same assembly and inherits SampleClass3,
                          'SampleClass3.MethodA, SampleClass3.MethodB,
                          'SampleClass3.MethodC and SampleClass3.MethodD      

        'Dim class4 As New SampleClass4() 'SampleClass4 is not accessible because
                                          'it is defined as friend and resides in
                                          'other assembly.
    End Sub

    Private Sub MethodB()
        'Doing MethodB stuff...
    End Sub

    Friend Sub MethodC()
        'Doing MethodC stuff...
    End Sub

    Protected Sub MethodD()
        'Doing MethodD stuff...
    End Sub

    Protected Friend Sub MethodE()
        'Doing MethodE stuff...
    End Sub
End Class

SampleClass2.vb：

Friend Class SampleClass2
    Public Sub MethodA()
        'Doing MethodA stuff...
    End Sub

    Private Sub MethodB()
        'Doing MethodB stuff...
    End Sub

    Friend Sub MethodC()
        'Doing MethodC stuff...
    End Sub

    Protected Sub MethodD()
        'Doing MethodD stuff...
    End Sub

    Protected Friend Sub MethodE()
        'Doing MethodE stuff...
    End Sub
End Class

SampleClass3.vb：

Public Class SampleClass3
    Public Sub MethodA()
        'Doing MethodA stuff...
    End Sub
    Private Sub MethodB()
        'Doing MethodB stuff...
    End Sub

    Friend Sub MethodC()
        'Doing MethodC stuff...
    End Sub

    Protected Sub MethodD()
        'Doing MethodD stuff...
    End Sub

    Protected Friend Sub MethodE()
        'Doing MethodE stuff...
    End Sub
End Class

SampleClass4.vb：

Friend Class SampleClass4
    Public Sub MethodA()
        'Doing MethodA stuff...
    End Sub
    Private Sub MethodB()
        'Doing MethodB stuff...
    End Sub

    Friend Sub MethodC()
        'Doing MethodC stuff...
    End Sub

    Protected Sub MethodD()
        'Doing MethodD stuff...
    End Sub

    Protected Friend Sub MethodE()
        'Doing MethodE stuff...
    End Sub
End Class