IComparer based on property of an interface

Question

I have created a class Car that derives form the abstract class TransportMeans and implements an interface PrivateMeans which contains only one property:

interface PrivateMean 
{
int capacity { set; get; }
}

I want to implement a class thet sorts the objects of the class Car according to the property capacity. I want to do this by the use of the interface IComparer.

However, when I declare an additonal class CarComparer as follows:

public class CarComparer : IComparer<Car>
{

    int IComparer<Car>.Comparer(Car obj1, Car obj2)
    {
        PrivateMean t1 = (PrivateMean)obj1;
        PrivateMean t2 = (PrivateMean)obj2;


        if (t1 != null && t2 != null)
        {
            if (t1.capacity >= t2.capacity)
                return 1;
            else return -1;
        }
        else
            throw new ArgumentException("Some Parameter is not a Car!");
    }
}

I receive the error :

Error 1 'MeansOfTransport.CarComparer' does not implement interface member 'System.Collections.Generic.IComparer.Compare(MeansOfTransport.Car, MeansOfTransport.Car)'.

What is the problem?

Furthermore I am not allowed to use IComparer without a type definition (Car). Why?

`IComparer` and `IComparer` are different interfaces. The text of your question mentions one, while the code uses the other. If you want to use the non-templated version `IComparer`, you need to remove `` where you state the implemented interfaces, from where you implement the interface, and change the type parameters in the implementation to `object`. — Eric J., Feb 21 '12 at 17:31

score 2 · Accepted Answer · answered Feb 21 '12 at 17:31

2

You have

int IComparer<Car>.Comparer(Car obj1, Car obj2)

You probably meant

int IComparer<Car>.Compare(Car obj1, Car obj2)

answered Feb 21 '12 at 17:31

500 - Internal Server Error

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score 0 · Answer 2 · answered Feb 21 '12 at 17:34

0

Possible problems:

You need to implement a Compare method, but yours is called Comparer
The method you are implementing is public, so yours should be too. Currently your method has no access modifier, so it will default to internal.

answered Feb 21 '12 at 17:34

raveturned

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IComparer based on property of an interface

2 Answers2