当接口ReadOnly属性在C＃.NET中有效时，为什么不能在VB.NET中覆盖它？ [英] Why can't Interface ReadOnly properties be overridden in VB.NET, when it is valid in C#.NET?

问题描述

（这与另一个问题）

如果您定义了一个接口，其中只有一个吸气剂的属性（在VB.NET中为ReadOnly）， 为什么您可以在使用C＃而不是VB来实现类中定义setter ？

If you define an Interface where there is a Property with only a getter (= ReadOnly in VB.NET), why can you define the setter in implementing classes with C# but not with VB ?

我以为它是在.NET级别定义的，

I would have thought it was defined at .NET level, and not language-specific.

示例：对于此界面

'VB.NET
Interface SomeInterface

    'the interface only say that implementers must provide a value for reading
    ReadOnly Property PublicProperty As String

End Interface

或

//C# code
interface IPublicProperty
{
    string PublicProperty { get; }
}

这是C＃中的正确实现：

This is a correct implementation in C# :

public class Implementer:IPublicProperty
    {
        private string _publicProperty;

        public string PublicProperty
        {
            get
            {
                return _publicProperty;
            }
            set
            {
                _publicProperty = value;
            }
        }
    }

但这在VB中无效.NET

But this is invalid in VB.NET

Public Property PublicProperty As String Implements SomeInterface.PublicProperty
    Get
        Return _myProperty
    End Get
    Set(ByVal value As String)
        _myProperty = value
    End Set
End Property

---

更新2015/04/23

事实证明，此功能是VB14的一部分！
参见语言C＃6和VB 14 和 Visual Basic 14中的新语言功能中的功能：

Turns out this feature is coming as part of VB14 ! See Languages features in C# 6 and VB 14 and New Language Features in Visual Basic 14 :

ReadWrite道具可以实现ReadOnly接口属性
可以清除语言的古怪之处。看下面的示例：

ReadOnly interface properties can be implemented by ReadWrite props This cleans up a quirky corner of the language. Look at this example:

Interface I
    ReadOnly Property P As Integer
End Interface


Class C : Implements I
    Public Property P As Integer Implements I.P
End Class

以前，如果要实现ReadOnly属性IP，则
也必须使用ReadOnly属性实现。既然
的限制已经放宽了：您可以根据需要使用读/写
属性来实现它。这个例子碰巧是通过
读/写autoprop来实现的，但是您也可以使用带有getter和
setter的属性。

Previously, if you were implementing the ReadOnly property I.P, then you had to implement it with a ReadOnly property as well. Now that restriction has been relaxed: you can implement it with a read/write property if you want. This example happens to implement it with a read/write autoprop, but you can also use a property with getter and setter.

推荐答案

请小心地假设VB.NET和C＃是同一语言，但口音不同。

Be careful assuming that VB.NET and C# are the same language spoken with a different accent - they're not.

因为VB.NET要求接口成员的实现必须具有 Implements 子句，从而说明要实现的成员。 C＃使您可以显式（类似于VB.NET）或隐式（无VB.NET等效）实现接口成员。因此，此 actual C＃版本是

Because VB.NET requires implementation of an interface member to have that Implements clause, saying which member it is implementing. C# lets you implement interface members explicitly (SORT OF like VB.NET), or implicitly (no VB.NET equivalent). Therefore the actual C# version of this is

public class Implementer : IPublicProperty
{
    private string _publicProperty;

    string IPublicProperty.PublicProperty    // explicit implementation
    {
        get
        {
            return _publicProperty;
        }
        set
        {
            _publicProperty = value;
        }
    }
}

给出错误：

and this does gives an error:

错误CS0550： ConsoleApplication171.Implementer.ConsoleApplication171.IPublicProperty.PublicProperty.set添加的访问器不是在接口成员'ConsoleApplication171.IPublicProperty.PublicProperty'中找到

error CS0550: 'ConsoleApplication171.Implementer.ConsoleApplication171.IPublicProperty.PublicProperty.set' adds an accessor not found in interface member 'ConsoleApplication171.IPublicProperty.PublicProperty'

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