Csharp/CSharp Tutorial/Data Structure/Array Index

Assigning array reference variables

<source lang="csharp">using System;

class MainClass {

 public static void Main() {  
   int i; 

   int[] nums1 = new int[10]; 
   int[] nums2 = new int[10]; 

   for(i=0; i < 10; i++) 
      nums1[i] = i; 

   for(i=0; i < 10; i++) 
      nums2[i] = -i; 

   Console.Write("Here is nums1: "); 
   for(i=0; i < 10; i++) 
     Console.Write(nums1[i] + " ");   
   Console.Write("Here is nums2: "); 
   for(i=0; i < 10; i++) 
     Console.Write(nums2[i] + " ");   
   Console.WriteLine(); 

   nums2 = nums1; // now nums2 refers to nums1 

   Console.Write("Here is nums2 after assignment: "); 
   for(i=0; i < 10; i++) 
     Console.Write(nums2[i] + " ");   
   Console.WriteLine(); 
 }  

}</source>

Here is nums1: 0 1 2 3 4 5 6 7 8 9 Here is nums2: 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
Here is nums2 after assignment: 0 1 2 3 4 5 6 7 8 9

Demonstrate an array overrun

<source lang="csharp">using System;

class MainClass {

 public static void Main() {  
   int[] sample = new int[10]; 
   int i;  
 
   // generate an array overrun 
   for(i = 0; i < 100; i = i+1)  
     sample[i] = i; 
 }  

}</source>

Unhandled Exception: System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at MainClass.Main()

Set array element value by index(subscript)

<source lang="csharp">using System;

class MainClass {

 public static void Main() {  
   int[] nums = new int[10]; 
   int avg = 0; 

   nums[0] = 99; 
   nums[1] = 10; 
   nums[2] = 100; 
   nums[3] = 18; 
   nums[4] = 78; 
   nums[5] = 23; 
   nums[6] = 63; 
   nums[7] = 9; 
   nums[8] = 87; 
   nums[9] = 49; 

   for(int i=0; i < 10; i++)  
     avg = avg + nums[i]; 

   avg = avg / 10; 

   Console.WriteLine("Average: " + avg); 
 }  

}</source>

Average: 53

Swapping Data between Positions in an Array

<source lang="csharp">class MainClass {

 static void Main()
 {
   string[] languages = new string[9]{"C#", "COBOL", "Java","C++"};
   string language = languages[3];
   languages[3] = languages[2];
   languages[2] = language;
 }

}</source>

Use the IndexOf() and LastIndexOf() methods to find the string "Hello" in stringArray

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string[] stringArray = {"Hello", "to", "everyone", "Hello", "all"};
   Console.WriteLine("stringArray:");
   for (int i = 0; i < stringArray.Length; i++)
   {
     Console.WriteLine("stringArray[" + i + "] = " + stringArray[i]);
   }

   int index = Array.IndexOf(stringArray, "Hello");
   Console.WriteLine("Array.IndexOf(stringArray, \"Hello\") = " + index);
   index = Array.LastIndexOf(stringArray, "Hello");
   Console.WriteLine("Array.LastIndexOf(stringArray, \"Hello\") = " + index);
 }

}</source>

stringArray:
stringArray[0] = Hello
stringArray[1] = to
stringArray[2] = everyone
stringArray[3] = Hello
stringArray[4] = all
Array.IndexOf(stringArray, "Hello") = 0
Array.LastIndexOf(stringArray, "Hello") = 3

Use the IndexOf() and LastIndexOf() methods to find the value 1 in intArray

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   int[] intArray = {1, 2, 1, 3};
   Console.WriteLine("intArray:");
   for (int i = 0; i < intArray.Length; i++)
   {
     Console.WriteLine("intArray[" + i + "] = " +
       intArray[i]);
   }
   
   int index = Array.IndexOf(intArray, 1);
   Console.WriteLine("Array.IndexOf(intArray, 1) = " + index);
   index = Array.LastIndexOf(intArray, 1);
   Console.WriteLine("Array.LastIndexOf(intArray, 1) = " + index);
 }

}</source>

intArray:
intArray[0] = 1
intArray[1] = 2
intArray[2] = 1
intArray[3] = 3
Array.IndexOf(intArray, 1) = 0
Array.LastIndexOf(intArray, 1) = 2