C# 0 The Complete Reference

Sorting and Searching Arrays

Often you will want to sort the contents of an array. To handle this, 

Array

 supports a rich 

complement of sorting methods. Using 

Sort( )

, you can sort an entire array, a range within 

an array or a pair of arrays that contain corresponding key/value pairs. Once an array has 

been sorted, you can efficiently search it using 

BinarySearch( )

. Here is a program that 

demonstrates the 

Sort( )

 and 

BinarySearch( )

 methods by sorting an array of 

int

s:

// Sort an array and search for a value.

using System;

class SortDemo {

  static void Main() {

    int[] nums = { 5, 4, 6, 3, 14, 9, 8, 17, 1, 24, -1, 0 };

    // Display original order.

    Console.Write("Original order: ");

    foreach(int i in nums)

      Console.Write(i + " ");

    Console.WriteLine();

    // Sort the array.

    Array.Sort(nums);

    // Display sorted order.

    Console.Write("Sorted order:   ");

    foreach(int i in nums)

      Console.Write(i + " ");

    Console.WriteLine();

    // Search for 14.

    int idx = Array.BinarySearch(nums, 14);

    Console.WriteLine("Index of 14 is " + idx);

  }

}

The output is shown here:

Original order: 5 4 6 3 14 9 8 17 1 24 -1 0

Sorted order:   -1 0 1 3 4 5 6 8 9 14 17 24

Index of 14 is 9

In the preceding example, the array has an element type of 

int

, which is a value type. 

All methods defined by 

Array

 are automatically available to all of the built-in value types. 

However, this may not be the case for arrays of object references. To sort or search an array 

of object references, the class type of those objects must implement either the 

IComparable

or

IComparable

 interface. If the class does not implement one of these interfaces, a 

runtime exception will occur when attempting to sort or search the array. Fortunately, both 

IComparable

 and 

IComparable

 are easy to implement.

IComparable

 defines just one method:

int CompareTo(object 

obj

)

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