In this program, You will learn how to find union and intersection of two arrays in C#.

```
1st list is: 1 2 3 4 5
2nd list is: 3 4 5
Union is: 1 2 3 4 5
Intersection is: 3 4 5
```

## Example: How to find union and intersection of two arrays in C#.

```
using System;
public class Program
{
static void printUnion(int[] arr1, int[] arr2, int len1, int len2)
{
int f, i, j, k = 0;
int[] arr3 = new int[100];
for (i = 0; i < len1; i++)
{
arr3[k] = arr1[i];
k++;
}
for (i = 0; i < len2; i++)
{
f = 0;
for (j = 0; j < len1; j++)
{
if (arr2[i] == arr1[j])
{
f = 1;
}
}
if (f == 0)
{
arr3[k] = arr2[i];
k++;
}
}
Console.Write("Union of Two Array is :");
for (i = 0; i < k; i++)
{
Console.Write(arr3[i] + " ");
}
}
static void printIntersection(int[] arr1, int[] arr2, int len1, int len2)
{
int[] arr3 = new int[100];
int i, j, k = 0;
for (i = 0; i < len1; i++)
{
for (j = 0; j < len2; j++)
{
if (arr1[i] == arr2[j])
{
arr3[k] = arr1[i];
k++;
}
}
}
Console.Write("\nIntersection of Two Array is :");
for (i = 0; i < k; i++)
{
Console.Write(arr3[i] + " ");
}
}
public static void Main(string[] args)
{
int[] arr1 = new int[5];
int[] arr2 = new int[3];
Console.Write("Enter first array elements:");
for (int i = 0; i < arr1.Length; i++)
{
arr1[i] = Convert.ToInt32(Console.ReadLine());
}
Console.Write("Enter second array elements:");
for (int i = 0; i < arr2.Length; i++)
{
arr2[i] = Convert.ToInt32(Console.ReadLine());
}
printUnion(arr1, arr2, arr1.Length, arr2.Length);
printIntersection(arr1, arr2, arr1.Length, arr2.Length);
}
}
```

#### Output:

```
Enter first array elements:10
20
30
40
50
Enter second array elements:30
40
50
Union of Two Array is :10 20 30 40 50
Intersection of Two Array is :30 40 50
```