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c#.netcompiler-errors
Ignas Laukineitis
Ignas Laukineitis

Reputation: 71

Does not implement System.IComparable.CompareTo(object)

Error 1 'Koordinates.Vieta' does not implement interface member 'System.IComparable.CompareTo(object)'

the code:

    public class Vieta : IComparable //error is thrown here, on "Vieta"
{
    public double x, y; 
    //constructor
    public Vieta(double a, double b)
    {
        x = a; y = b;
    }
    //read only parameter
    public double ilgis
    {
        get
        {
            return Math.Sqrt(x * x + y * y);
        }
    }

    public int CompareTo(Vieta other)
    {
        if (other == null) return 1;
        return other.ilgis.CompareTo(this.ilgis);
    }
}

Upvotes: 1

Views: 4515

Answers (2)

Frederik Gheysels
Frederik Gheysels

Reputation: 56934

You have a compare method that takes an instance of the Vieta class. The IComparable interface declares a method CompareTo(object) (note that the parameter should of type object).

It is offcourse better to have a strong typed CompareTo method. You could implement the IComparable<T> interface as well.

My suggestion would be to do that, and implement the IComparable interface explicitly. Then, you'll end up with something like this:

public class Vieta : IComparable, IComparable<Vieta>
{

    IComparable.CompareTo( object obj )
    {

       var other = obj as Vieta;

       if( other == null ) return false;

       return CompareTo(other);

    }


    public int CompareTo( Vieta other )
    {
         // Implement your compare logic here.
    }

}

By implementing the IComparable interface explicitly, the CompareTo(object) method will be hidden from intellisense. In fact, you'll only be able to call that method if you cast the class to the interface type (or if an instance of that class is passed to a method that takes an IComparable parameter, for instance).

Upvotes: 2

SomeWritesReserved
SomeWritesReserved

Reputation: 1075

Change the class to this:

public class Vieta : IComparable<Vieta>

IComparable defines an int CompareTo(object) while the generic IComparable<T> defines an int CompareTo(T).

Upvotes: 2

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