The IComparable Interface

You want to know when to implement the IComparable interface.

Implement the IComparable interface if you can compare instances of a type to each other.

If possible, make the CompareTo method public, and always account for null arguments.


class Triangle : IComparable {
    // In a real class, this would be a property.
    public double Side;

    // Compare triangles by their side property.
    public int CompareTo(object obj) {
        // Throw if other object can't be cast to Triangle.
        Triangle other = (Triangle) obj;

        // Any triangle is greater than a null triangle.
        if ( other == null || this.Side > other.Side ) {
            return 1;
        else if ( this.Side < other.Side ) {
            return -1;
        else {
            return 0;

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