Splitting Lists into Chunks of a Specified Size in C#

In many programming scenarios, such as batch processing or paging, it's necessary to split a list into smaller, more manageable chunks of a specified size. C# does not have a built-in method for this specific task, but you can easily implement this functionality using simple loops or LINQ. This article demonstrates how to split a list into chunks of size N in C#, providing both a basic and a LINQ-based approach.

Basic Approach Using a Loop

The simplest way to split a list into chunks of a specified size is by using a loop. This method is straightforward and doesn't require additional libraries.

Example: Splitting a List of Integers

Suppose you have a list of integers and you want to split this list into chunks of size N.

using System;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
        int chunkSize = 3;

        List<List<int>> chunks = new List<List<int>>();
        for (int i = 0; i < numbers.Count; i += chunkSize)
        {
            chunks.Add(numbers.GetRange(i, Math.Min(chunkSize, numbers.Count - i)));
        }

        foreach (var chunk in chunks)
        {
            Console.WriteLine($"Chunk: {string.Join(", ", chunk)}");
        }
        // Output will be:
        // Chunk: 1, 2, 3
        // Chunk: 4, 5, 6
        // Chunk: 7, 8, 9
        // Chunk: 10
    }
}

In this example, GetRange is used to create sublists, each of a specified size, from the original list. Math.Min ensures that you don't exceed the bounds of the list.

LINQ Approach

You can also use LINQ to achieve the same result in a more declarative style. This method is often more readable and concise.

Example: LINQ to Split List

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
        int chunkSize = 3;

        var chunks = numbers.Select((x, i) => new { Index = i, Value = x })
                            .GroupBy(x => x.Index / chunkSize)
                            .Select(x => x.Select(v => v.Value).ToList())
                            .ToList();

        foreach (var chunk in chunks)
        {
            Console.WriteLine($"Chunk: {string.Join(", ", chunk)}");
        }
        // Output will be:
        // Chunk: 1, 2, 3
        // Chunk: 4, 5, 6
        // Chunk: 7, 8, 9
        // Chunk: 10
    }
}

This LINQ query uses the Select method to project each element into a new object that includes the index, then groups by the result of integer division of the index by the chunk size. Each group is then transformed back into a list of integers.

Tips for Splitting Lists into Chunks

1. Choose the Right Method: If performance is a key concern, especially with very large lists, the loop method may be more efficient. For code readability and conciseness, the LINQ method is superior.
2. Handling Edge Cases: Always test your chunking logic with edge cases, such as empty lists or chunk sizes larger than the list itself.
3. Use Extensions: Consider encapsulating the chunking logic into an extension method for IEnumerable<T>, which can make your main code cleaner and more reusable.

Conclusion

Splitting a list into chunks of a specified size is a common requirement that can be efficiently handled using either basic loops or LINQ in C#. By understanding these techniques, developers can handle large data sets more effectively, improving the performance and scalability of C# applications.