我必须在 class 中实现函数的错误，即使函数已定义

Question

我收到错误：Class 'QueryParameterComparer' must implement 'Function Compare(x As QueryParameter, y As QueryParameter) As Integer' for interface 'System.Collections.Generic.IComparer(Of QueryParameter)'.

关于这个 class 定义：

    Protected Class QueryParameterComparer
        Implements IComparer(Of QueryParameter)

        Public Function Compare(x As QueryParameter, y As QueryParameter) As Integer
            If x.Name = y.Name Then
                Return String.Compare(x.Value, y.Value)
            Else
                Return String.Compare(x.Name, y.Name)
            End If
        End Function

    End Class

我也试过完整写出来：

    Protected Class QueryParameterComparer
        Implements System.Collections.Generic.IComparer(Of QueryParameter)

        Public Function Compare(x As QueryParameter, y As QueryParameter) As Integer
            If x.Name = y.Name Then
                Return String.Compare(x.Value, y.Value)
            Else
                Return String.Compare(x.Name, y.Name)
            End If
        End Function

    End Class

我错过了什么？

Answer 1

不像在 c# 中，方法的名称只需要与接口中的名称相匹配，在 VB.NET 中，所有接口实现必须始终在每个成员上用 Implements 关键字显式声明:

Protected Class QueryParameterComparer
    Implements IComparer(Of QueryParameter)

    Public Function Compare(x As QueryParameter, y As QueryParameter) As Integer Implements IComparer(Of QueryParameter).Compare
        ' ...
    End Function
End Class

Answer 2

VB.Net要求您指定哪些方法是您接口的实现方法。

Public Function Compare(x As QueryParameter, y As QueryParameter) As Integer Implements System.Collections.Generic.IComparer(Of QueryParameter).Compare

这很奇怪，但它确实允许您为实现指定不同的函数名称。这使得直接访问您的 class 可以有一个函数名称，但通过接口的引用将有接口方法名称。您可以做的另一件事是将方法指定为 Private，这样您就只能通过接口引用访问该方法。

我必须在 class 中实现函数的错误，即使函数已定义

Error that I must implement a function in a class even though function is defined

vb.net

interface

class

interface-implementation