.net - 当接口(interface) ReadOnly 属性在 C#.NET 中有效时，为什么不能在 VB.NET 中覆盖它？

Question

(这与 this other question 相关)

如果您定义一个接口(interface)，其中有一个仅具有 getter 的属性(= VB.NET 中的 ReadOnly)，为什么您可以在使用 C# 实现类时定义 setter，而不能使用 VB ？

我本以为它是在 .NET 级别定义的，而不是特定于语言的。

示例:对于此接口(interface)

'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:

public class Implementer:IPublicProperty
    {
        private string _publicProperty;

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

但这在VB.NET中是无效的

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

<小时/>

更新2015/04/23

原来这个功能是作为 VB14 的一部分出现的!请参阅Languages features in C# 6 and VB 14和 New Language Features in Visual Basic 14 :

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

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.

Answer 1

请小心假设 VB.NET 和 C# 是同一种语言，但口音不同 - 它们不是。

因为 VB.NET 要求接口(interface)成员的实现具有 Implements 子句，说明它正在实现哪个成员。 C# 允许您显式(类似于 VB.NET)或隐式(没有 VB.NET 等效项)实现接口(interface)成员。因此，实际 C# 版本是

public class Implementer : IPublicProperty
{
    private string _publicProperty;

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

这确实给出了一个错误:

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