C# — Generics

Generic class

public class Box<T>
{
    public T Content { get; set; }

    public Box(T content)
    {
        Content = content;
    }
}

var intBox = new Box<int>(42);
var strBox = new Box<string>("Hello");

Generic method

public static T Max<T>(T a, T b) where T : IComparable<T>
{
    return a.CompareTo(b) > 0 ? a : b;
}

Console.WriteLine(Max(10, 20));    // 20
Console.WriteLine(Max("a", "b"));  // b

Generic constraints

public class Repository<T> where T : class, IEntity
{
    public void Save(T entity) { }
    public T FindById(int id) => default;
}

// Multiple constraints
public class Cache<T> where T : class, ICloneable, new()
{
    public T CreateDefault() => new T();
}

Generic interface

public interface IRepository<T>
{
    void Add(T item);
    T GetById(int id);
    IEnumerable<T> GetAll();
}

Mini Practice

Write C# code that:

1. Creates a generic class
2. Uses generic constraints
3. Implements a generic interface
4. Creates a generic method

Up Next

In the next lesson, you'll learn about LINQ — querying collections.