C# in a Nutshell, Second Edition

Name

IComparable

Synopsis

This interface is implemented by classes that can be ordered in a list. Classes such as String and Int32 implement this interface. You can also implement it in your own classes to create a type-specific method that allows your objects to be sorted in arrays. This interface does not allow classes to be compared with the greater-than and less-than operators; that requires operator overloading. This interface simply provides a well-known protocol for doing comparisons of objects. (Of course, nothing prevents a C# programmer from defining overloaded comparison operations and calling CompareTo( ) as the implementation.)

To implement IComparable, override the CompareTo( ) method. This method accepts another instance of your IComparable object and returns an integer that indicates the result of the comparison. (Zero means equal, less than zero indicates that the supplied object is less than the current instance, and greater than zero indicates that the object is greater than the current instance.) Note that the actual value of the integer is irrelevant other than its positive, negative, or zero status (similar to the way strcmp works in C). Also note that because CompareTo( ) accepts an argument of IComparable type, care must be taken to ensure that it is a legitimate comparison—for example, myInt.CompareTo(myString) throws an ArgumentException.

public interface IComparable {
// Public Instance Methods
   public int CompareTo(object obj);
}

Implemented By

Multiple types ...