C# 0 The Complete Reference

PART II

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This method compares the invoking object against the value in 

obj.

 It returns greater than 

zero if the invoking object is greater than 

obj,

 zero if the two objects are equal, and less than 

zero if the invoking object is less than 

obj.

IComparable

 is the generic version of 

IComparable

. It defines the generic version 

of

CompareTo( )

:

int CompareTo(T 

obj

)

The generic version of 

CompareTo( )

 works like the non-generic version. It compares 

the invoking object against the value in 

obj.

 It returns greater than zero if the invoking object 

is greater than 

obj,

 zero if the two objects are equal, and less than zero if the invoking object 

is less than 

obj.

 The advantage of using 

IComparable

is type safety because the type of 

data being operated upon is explicitly specified. There is no need to cast the object being 

compared from 

object

into the desired type. Here is an example that illustrates sorting and 

searching an array of user-defined class objects:

// Sort and search an array of objects.

using System;

class MyClass : IComparable {

  public int i;

  public MyClass(int x) { i = x; }

  // Implement IComparable.

  public int CompareTo(MyClass v) {

    return i - v.i;

  }

  public bool Equals(MyClass v) {

    return i == v.i;

  }

}

class SortDemo {

  static void Main() {

    MyClass[] nums = new MyClass[5];

    nums[0] = new MyClass(5);

    nums[1] = new MyClass(2);

    nums[2] = new MyClass(3);

    nums[3] = new MyClass(4);

    nums[4] = new MyClass(1);

    // Display original order.

    Console.Write("Original order: ");

    foreach(MyClass o in nums)

      Console.Write(o.i + " ");

    Console.WriteLine();

    // Sort the array.

    Array.Sort(nums);

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    // Display sorted order.

    Console.Write("Sorted order:   ");

    foreach(MyClass o in nums)

      Console.Write(o.i + " ");

    Console.WriteLine();

    // Search for MyClass(2).

    MyClass x = new MyClass(2);

    int idx = Array.BinarySearch(nums, x);

    Console.WriteLine("Index of MyClass(2) is " + idx);

  }

}

The output is shown here:

Original order: 5 2 3 4 1

Sorted order:   1 2 3 4 5

Index of MyClass(2) is 1