问题
I get the error: Class 'QueryParameterComparer' must implement 'Function Compare(x As QueryParameter, y As QueryParameter) As Integer' for interface 'System.Collections.Generic.IComparer(Of QueryParameter)'.
On this class definition:
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
I also tried writing it out fully:
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
What am I missing?
回答1:
Unlike in c#, where the name of the method just has to match the one in the interface, in VB.NET, all interface implementations must always be explicitly stated with Implements
keywords on each member:
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
回答2:
VB.Net requires you to specify which methods are the implementation methods of your interfaces.
Public Function Compare(x As QueryParameter, y As QueryParameter) As Integer Implements System.Collections.Generic.IComparer(Of QueryParameter).Compare
It's odd, but it does allow for you to specify a different function name for the implementation. This makes it so that a direct access to your class can have one name for the function, but a reference through the interface would have the interface method name. Something else you can do is specify the method a Private so that you can only access the method through an interface reference.
来源:https://stackoverflow.com/questions/30328991/error-that-i-must-implement-a-function-in-a-class-even-though-function-is-define