How Can I Efficiently Chunk a List into Sublists of a Specific Size in C#?

Dividing a List into Smaller Sublists of a Specified Size in C#

The original splitList function aimed to break down a list into smaller lists, each containing 30 elements. However, it had flaws resulting in sublists of inconsistent sizes.

Improved Solution using an Extension Method:

A more robust approach involves creating a C# extension method:

public static class ListExtensions
{
    public static List<List<T>> ChunkBy<T>(this List<T> source, int chunkSize)
    {
        return source
            .Select((x, i) => new { Index = i, Value = x })
            .GroupBy(x => x.Index / chunkSize)
            .Select(x => x.Select(v => v.Value).ToList())
            .ToList();
    }
}

Functionality Explained:

This extension method efficiently chunks a list (source) into sublists of a given chunkSize. It leverages LINQ:

1. Indexing and Value Pairing: Select((x, i) => new { Index = i, Value = x }) creates an anonymous type containing each element's index and value.

2. Grouping by Chunk: GroupBy(x => x.Index / chunkSize) groups elements based on their index divided by the chunkSize. This ensures elements within the same chunk are grouped together.

3. List Creation: Select(x => x.Select(v => v.Value).ToList()) converts each group back into a list of the original element type.

4. Final List of Lists: ToList() creates the final list containing the chunked sublists.

Practical Application:

To use this method to create sublists of size 30 from a list named locations:

List<List<YourElementType>> chunkedLists = locations.ChunkBy(30);

Illustrative Example:

If locations contains 144 elements, chunkedLists will correctly contain 5 sublists with sizes: 30, 30, 30, 30, and 24.

Future C# Enhancement:

Note that .NET 6 introduces a built-in Chunk method for this purpose, simplifying the process further:

const int PAGE_SIZE = 5;
IEnumerable<Movie> chunks = movies.Chunk(PAGE_SIZE);

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