AutoCollection

Actions	NuGet

A lightweight source generator library that automatically creates read-only collection wrappers for your types using the GenerateReadOnlyList attribute.

Overview

AutoCollection eliminates boilerplate code by generating IReadOnlyList<T> implementations for your collection types. This allows you to create type-safe, immutable collection wrappers without writing repetitive code.

Installation

Install the AutoCollection package via NuGet:

dotnet add package AutoCollection

Usage

AutoCollection provides a simple attribute-based API to generate read-only list implementations. There are two main ways to use this library:

1. Basic Usage with Default Implementation

Simply apply the attribute to a partial class and the source generator will create a complete implementation:

using AutoCollection;

namespace Example;

// Apply the attribute to a partial class
[GenerateReadOnlyList(typeof(string))]
public partial class SimpleStringList { }

// Usage:
var stringList = new SimpleStringList(["one", "two", "three"]);
Console.WriteLine(stringList.Count);    // Outputs: 3
Console.WriteLine(stringList[0]);       // Outputs: "one"

2. Custom Implementation with Named Backing Field

You can specify a custom backing field name and provide your own constructor:

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

namespace Example;

[GenerateReadOnlyList(typeof(int), nameof(_values))]
public partial class CustomIntList
{
    public CustomIntList(IEnumerable<int> vals)
    {
        _values = vals?.ToArray() ?? throw new ArgumentNullException(nameof(vals));
    }

    private readonly int[] _values;
}

// Usage:
var intList = new CustomIntList([1, 2, 3]);
Console.WriteLine(intList.Count);    // Outputs: 3
Console.WriteLine(intList[1]);       // Outputs: 2

3. Working with Complex Types

The generator works with any type, including your own custom classes:

using AutoCollection;

namespace Example;

public class Person
{
    public string FirstName { get; set; } = "John";
    public string LastName { get; set; } = "Doe";
    public string FullName => $"{FirstName} {LastName}";
}

[GenerateReadOnlyList(typeof(Person))]
public partial class PersonList { }

// Usage:
var people = new PersonList([new Person(), new Person()]);
Console.WriteLine(people.Count);              // Outputs: 2
Console.WriteLine(people[0].FullName);        // Outputs: "John Doe"

4. Basic Usage for IList

using AutoCollection;

namespace Example;

// Apply the attribute to a partial class
[GenerateList(typeof(string))]
public partial class SimpleStringList { }

// Usage:
var stringList = new SimpleStringList(["one", "two", "three"]);
Console.WriteLine(stringList.Count);    // Outputs: 3
Console.WriteLine(stringList[0]);       // Outputs: "one"
stringList.Add("Four");
Console.WriteLine(stringList[3]);       // Outputs: "four"

Features

Zero runtime dependencies - AutoCollection runs at build time through the C# source generator feature
Type safety - Get compile-time checking for your collections
Customizable - Use default implementation or provide your own backing field and constructor
Lightweight - Generates minimal code with no performance overhead

Generated Code

For a class like:

[GenerateReadOnlyList(typeof(string))]
public partial class SimpleStringList { }

The source generator creates:

public partial class SimpleStringList : IReadOnlyList<string>
{
    public SimpleStringList(IEnumerable<string> items)
    {
        _items = items?.ToArray() ?? throw new ArgumentNullException(nameof(items));
    }

    private readonly string[] _items;

    public string this[int index] => _items[index];
    public int Count => _items.Length;

    public IEnumerator<string> GetEnumerator() => ((IEnumerable<string>)_items).GetEnumerator();
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => _items.GetEnumerator();
}

Requirements

.NET 6.0 or higher
C# 10.0 or higher

License

AutoCollection is licensed under the MIT License.

Contributing

Contributions are welcome! Feel free to submit issues or pull requests on the GitHub repository.

ChaseFlorell/AutoCollection