Convert a List of Lists to a 2D array in C#

This post will discuss how to convert a List of Lists to a 2D array in C#.

You can use LINQ to convert a List<List<T>> into a two-dimensional array T[][]. The following code example uses the Select() method to project each list into an array with the help of the ToArray() method.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<List<string>> lists = new List<List<string>>()

{

new List<string>() { "C", "C++" },

new List<string>() { "Java", "C#", "Kotlin" }

};

string[][] arrays = lists.Select(a => a.ToArray()).ToArray();

// print the 2D array

foreach (var array in arrays) {

Console.WriteLine(String.Join(", ", array));

}

Download Run Code

Output:

C, C++
Java, C#, Kotlin

If you need a T[,] instead, the best solution would probably be to loop through the list using nested loops and explicitly generate the 2D array.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<List<string>> lists = new List<List<string>>()

{

new List<string>() { "C", "C++" },

new List<string>() { "Java", "Kotlin" }

};

string[,] arrays = new string[lists.Count, lists[0].Count];

for (int i = 0; i < lists.Count; i++)

{

for (int j = 0; j < lists[i].Count; j++) {

arrays[i,j] = lists[i][j];

}

// print the 2D array

foreach (var array in arrays) {

Console.WriteLine(String.Join(", ", array));

}

Download Run Code

Output:

C
C++
Java
Kotlin

That’s all about converting a List of Lists to a 2D array in C#.

Convert a List of Lists to a 2D array in C#

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