CODEWITHSUNDEEP
c#nuniticomparable
Anonymous Coward
Anonymous Coward

Reputation: 886

C#: IComparable implementation private

I'm new to C# so this might be a really dump question: I implemented IComparable in my class and want to test it with NUnit. But the CompareTo-Method is marked as private and thus not accessible from the test.
What's the reason for this and how can I fix this?

The IComparable:

 
public class PersonHistoryItem : DateEntity,IComparable
    {
     ...
        int IComparable.CompareTo(object obj)
        {
            PersonHistoryItem phi = (PersonHistoryItem)obj;
            return this.StartDate.CompareTo(phi.StartDate);
        }
    }

The test: 

 
        [TestMethod]
        public void TestPersonHistoryItem() {
            DateTime startDate = new DateTime(2001, 2, 2);
            DateTime endDate = new DateTime(2010, 2, 2);
            PersonHistoryItem phi1 = new PersonHistoryItem(startDate,endDate);



        PersonHistoryItem phi2 = new PersonHistoryItem(startDate, endDate);

        Assert.IsTrue(phi1.CompareTo(phi2)==0);
    }

Upvotes: 1

Views: 1037

Answers (6)

Klaus Byskov Pedersen
Klaus Byskov Pedersen

Reputation: 120917

In C# an interface does not define accessors, so you can make your CompareTo method public and change the explicit interface implementation from:

int IComparable.CompareTo(object obj)

To:

public int CompareTo(object obj)

Upvotes: 0

Rob van Groenewoud
Rob van Groenewoud

Reputation: 1874

I think the easiest way would be to use implicit interface implementation:

public class PersonHistoryItem : DateEntity, IComparable
{
    ...
    public int CompareTo(object obj)
    {
        PersonHistoryItem phi = (PersonHistoryItem)obj;
        return this.StartDate.CompareTo(phi.StartDate);
    }
}

Upvotes: 1

Thibault Falise
Thibault Falise

Reputation: 5885

The main problem here is that you explicitly implements the CompareTo method, which only allows you to use it when you use your object as a IComparable object.

To correct the problem, specify the visibility as public and implement the CompareTo method not "explicitly" :

public class PersonHistoryItem : DateEntity,IComparable
{
    ...

    public int CompareTo(object obj)
    {
        PersonHistoryItem phi = (PersonHistoryItem)obj;
        return this.StartDate.CompareTo(phi.StartDate);
    }
}

Upvotes: 0

Adrian Zanescu
Adrian Zanescu

Reputation: 8008

Your approach uses explicit interface implementation. That means that the interface methods will not show up on your class unless a cast is done. Do this:((IComparable)phi1).CompareTo(phi2)

Upvotes: 0

Darin Dimitrov
Darin Dimitrov

Reputation: 1038710

var p1 = (IComparable)phi1;
var p2 = (IComparable)phi2;

Assert.IsTrue(p1.CompareTo(p2) == 0);

Upvotes: 1

Mark Seemann
Mark Seemann

Reputation: 233125

They are not private, they are just explicitly implemented. Declaring your variables as IComparable should solve the problem:

[TestMethod]
public void TestPersonHistoryItem() {
    DateTime startDate = new DateTime(2001, 2, 2);
    DateTime endDate = new DateTime(2010, 2, 2);
    IComparable phi1 = new PersonHistoryItem(startDate,endDate);

    IComparable phi2 = new PersonHistoryItem(startDate, endDate);

    Assert.IsTrue(phi1.CompareTo(phi2)==0);
}

Upvotes: 3

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