We have many ways to merge the two arrays in C# using the below methods,

• Using Array.Copy()
• Using Array.CopyTo()
• Using Array.Resize()
• Using AddRange() 

Merge two Arrays using Array.Copy()

The Array.Copy() method copies a range of elements from one array to another array. In the below example, we used the Array.Copy() method to copy the both the array elements into another array.

using System;

namespace MergeTwoArrays
{
    class Program
    {
        static void Main()
        {
            int[] firstArray = { 100, 200, 300, 400 };
            int[] secondArray = { 500, 600, 700, 800 };

            int[] result = new int[firstArray.Length + secondArray.Length];
            Array.Copy(firstArray, result, firstArray.Length);
            Array.Copy(secondArray, 0, result, firstArray.Length, secondArray.Length);

            Console.WriteLine(String.Join(",", result));
            Console.ReadKey();
        }
    }
}

Output:

100,200,300,400,500,600,700,800

Merge two Arrays using Array.CopyTo()

The Array.CopyTo() method is used to copy an array in C#. In the below example, we are copying all the arrays to empty arrays using CopyTo() method.

using System;
using System.Collections.Generic;

namespace MergeTwoArrays
{
    class Program
    {
        static void Main()
        {
            int[] firstArray = { 100, 200, 300, 400 };
            int[] secondArray = { 500, 600, 700, 800 };

        
            int[] result = new int[firstArray.Length + secondArray.Length];
            firstArray.CopyTo(result, 0);
            secondArray.CopyTo(result, firstArray.Length);

            Console.WriteLine(String.Join(",", result));
            Console.ReadKey();
        }
    }
}

  Output:

100,200,300,400,500,600,700,800

Merge two Arrays using Array.Resize()

The Array.Resize() method is used to resize a one-dimensional array in C#. In this example, we use Array.Resize() with Array.Copy() methods to copy the two arrays.

using System;

namespace MergeTwoArrays
{
    class Program
    {
        static void Main()
        {
            int[] firstArray = { 100, 200, 300, 400 };
            int[] secondArray = { 500, 600, 700 };

            int firstArrayLength = firstArray.Length;
            Array.Resize<int>(ref firstArray, firstArray.Length + secondArray.Length);
            Array.Copy(secondArray, 0, firstArray, firstArrayLength, secondArray.Length);

            Console.WriteLine(String.Join(",", firstArray));
            Console.ReadKey();
        }
    }
}

Output:

100,200,300,400,500,600,700

Merge two Arrays using AddRange() 

The AddRange() method is used to add the specified array elements at the end of the List<T>. The following example demonstrates how to add the 2 arrays using AddRange() method.

using System;
using System.Collections.Generic;

namespace MergeTwoArrays
{
    class Program
    {
        static void Main()
        {
            int[] firstArray = { 100, 200, 300, 400 };
            int[] secondArray = { 500, 600 };

            List<int> listOfArray = new List<int>(firstArray.Length + secondArray.Length);
            listOfArray.AddRange(firstArray);
            listOfArray.AddRange(secondArray);

            Console.WriteLine(String.Join(",", listOfArray.ToArray()));
            Console.ReadKey();
        }
    }
}

Output:

100,200,300,400,500,600