Split a List into sublists of size n in C#

This post will discuss how to split a list into sublists of size n in C#.

1. Using `Enumerable.GroupBy()` method

In LINQ, you can use the Enumerable.GroupBy() method to partition a list into multiple sublists. It groups the elements of a sequence according to a specified key selector function. The following code example demonstrates how the combination of Select() and GroupBy() method can break a list into the sublists according to the specified chunk size:

using System;

using System.Linq;

using System.Collections.Generic;

public static class Extensions

{

public static List<List<T>> partition<T>(this List<T> values, int chunkSize)

{

return values.Select((x, i) => new { Index = i, Value = x })

.GroupBy(x => x.Index / chunkSize)

.Select(x => x.Select(v => v.Value).ToList())

.ToList();

}

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

List<List<int>> partitions = values.partition(2);

foreach (List<int> partition in partitions) {

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

}

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Output:

1, 2
3, 4
5

2. Using `List<T>.GetRange()` method

The List<T>.GetRange() method is used to get elements between the desired range from a List<T>. The following example demonstrates the usage of the List<T>.GetRange() method for splitting a List<T> into specified number of chunks of equal sizes.

using System;

using System.Linq;

using System.Collections.Generic;

public static class Extensions

{

public static IEnumerable<List<T>> partition<T>(this List<T> values, int chunkSize)

{

for (int i = 0; i < values.Count; i += chunkSize) {

yield return values.GetRange(i, Math.Min(chunkSize, values.Count - i));

}

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

var partitions = values.partition(2);

foreach (List<int> partition in partitions) {

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

}

Download Run Code

Output:

1, 2
3, 4
5

The above generic extension method returns an IEnumerable. To return a List instead, do as follows:

using System;

using System.Collections.Generic;

public static class Extensions

{

public static List<List<T>> partition<T>(this List<T> values, int chunkSize)

{

var partitions = new List<List<T>>();

for (int i = 0; i < values.Count; i += chunkSize) {

partitions.Add(values.GetRange(i, Math.Min(chunkSize, values.Count - i)));

}

return partitions;

}

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

var partitions = values.partition(2);

foreach (List<int> partition in partitions) {

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

}

Download Run Code

Output:

1, 2
3, 4
5

3. Using `Enumerable.Take()` method

Alternatively, you can use the Enumerable.Take() method to split a list of items into chunks of a specific size. The Take() method returns a specified number of contiguous elements from the start of a sequence, and can be used as follows:

using System;

using System.Linq;

using System.Collections.Generic;

public static class Extensions

{

public static IEnumerable<IEnumerable<T>> partition<T>(this IEnumerable<T> values, int chunkSize)

{

while (values.Any())

{

yield return values.Take(chunkSize).ToList();

values = values.Skip(chunkSize).ToList();

}

public class Example

{

public static void Main()

{

List<int> values = new List<int>() { 1, 2, 3, 4, 5 };

var partitions = values.partition(2);

foreach (List<int> partition in partitions) {

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

}

Download Run Code

Output:

1, 2
3, 4
5

That’s all about splitting a list into sublists of size n in C#.

Split a List into sublists of size n in C#

1. Using Enumerable.GroupBy() method

2. Using List<T>.GetRange() method

3. Using Enumerable.Take() method

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1. Using `Enumerable.GroupBy()` method

2. Using `List<T>.GetRange()` method

3. Using `Enumerable.Take()` method