Combine two arrays in C#

Combining two arrays in C# can be accomplished using various methods. The most common approaches include using List.AddRange() method, Array.Copy(), or LINQ's Concat() method.

Syntax

Using List.AddRange() method −

var list = new List<T>();
list.AddRange(array1);
list.AddRange(array2);
T[] combinedArray = list.ToArray();

Using Array.Copy() method −

T[] combinedArray = new T[array1.Length + array2.Length];
Array.Copy(array1, 0, combinedArray, 0, array1.Length);
Array.Copy(array2, 0, combinedArray, array1.Length, array2.Length);

Using LINQ Concat() method −

T[] combinedArray = array1.Concat(array2).ToArray();

Using List.AddRange() Method

This approach creates a List, adds both arrays using AddRange(), then converts back to an array −

using System;
using System.Collections.Generic;

class Demo {
   static void Main() {
      int[] arr1 = { 37, 45, 65 };
      int[] arr2 = { 70, 89, 118 };
      
      Console.WriteLine("Array 1: " + string.Join(", ", arr1));
      Console.WriteLine("Array 2: " + string.Join(", ", arr2));
      
      var myList = new List<int>();
      myList.AddRange(arr1);
      myList.AddRange(arr2);
      
      int[] combinedArray = myList.ToArray();
      Console.WriteLine("Combined Array: " + string.Join(", ", combinedArray));
   }
}

The output of the above code is −

Array 1: 37, 45, 65
Array 2: 70, 89, 118
Combined Array: 37, 45, 65, 70, 89, 118

Using Array.Copy() Method

This method creates a new array with the exact size needed and copies elements directly −

using System;

class Demo {
   static void Main() {
      string[] fruits1 = { "Apple", "Banana" };
      string[] fruits2 = { "Orange", "Mango", "Grape" };
      
      Console.WriteLine("First Array: " + string.Join(", ", fruits1));
      Console.WriteLine("Second Array: " + string.Join(", ", fruits2));
      
      string[] combinedFruits = new string[fruits1.Length + fruits2.Length];
      Array.Copy(fruits1, 0, combinedFruits, 0, fruits1.Length);
      Array.Copy(fruits2, 0, combinedFruits, fruits1.Length, fruits2.Length);
      
      Console.WriteLine("Combined Array: " + string.Join(", ", combinedFruits));
   }
}

The output of the above code is −

First Array: Apple, Banana
Second Array: Orange, Mango, Grape
Combined Array: Apple, Banana, Orange, Mango, Grape

Using LINQ Concat() Method

LINQ provides the most concise approach using the Concat() extension method −

using System;
using System.Linq;

class Demo {
   static void Main() {
      double[] numbers1 = { 1.5, 2.7, 3.9 };
      double[] numbers2 = { 4.1, 5.3 };
      
      Console.WriteLine("Array 1: " + string.Join(", ", numbers1));
      Console.WriteLine("Array 2: " + string.Join(", ", numbers2));
      
      double[] combinedNumbers = numbers1.Concat(numbers2).ToArray();
      Console.WriteLine("Combined Array: " + string.Join(", ", combinedNumbers));
   }
}

The output of the above code is −

Array 1: 1.5, 2.7, 3.9
Array 2: 4.1, 5.3
Combined Array: 1.5, 2.7, 3.9, 4.1, 5.3

Performance Comparison

Conclusion

C# offers multiple ways to combine arrays: Array.Copy() for best performance, List.AddRange() for general use, and LINQ's Concat() for concise code. Choose the method based on your specific performance requirements and coding preferences.