Examples for the "Ignore Null Strategies" post: https://porg.es/ignore-null-strategies/

0-producer.cs

interface IProducer
{
    Result Produce();
}

class ProducerExample
{
    readonly IProducer _producer;

    // constructor elided...

    public Result Act()
    {
        if (_producer == null)
        {
            return Result.Default;
        }

        return _producer.Produce();
    }
}

1-handler.cs

interface IHandler
{
    void Handle();
}

class HandlerExample
{
    readonly IHandler _handler;

    // constructor elided...

    public void Run()
    {
        if (_handler == null)
        {
            // some other implementation
        }
        else
        {
            _handler.Handle();
        }
    }
}

2-producer2.cs

class DefaultProducer : IProducer
{
    public Result Produce() => Result.Default;
}

class ProducerExampleRevised
{
    [NotNull] readonly IProducer _strategy;

    // constructor elided...

    public Result Run()
    {
        return _strategy.Produce();
    }
}

3-producer2-2.cs

class ConstantProducer : IProducer
{
    public Result Value { get; }
    
    public ConstantProducer(Result value)
    {
        Value = value;
    }

    public Result Produce() => Value;
}

4-handler2.cs

class NullHandler : IHandler
{
    public void Handle() { }
}

class HandlerExampleRevised
{
    [NotNull] readonly IHandler _handler;

    // constructor elided...

    public void Run()
    {
        _handler.Handle();
    }
}

5-producer-functional.cs

delegate Result Producer();

static class Producers
{
    // Default is a Producer
    public static Result Default() => Result.Default;

    // Constant returns a Producer, given an argument
    public static Producer Constant(Result r) => () => r;
}

class FunctionalProducerExample
{
    [NotNull] readonly Producer _strategy;

    // constructor elided...

    public Result Run()
    {
        return _strategy();
    }
}

6-handler-functional.cs

delegate void Handler();

static class Handlers
{
    // Null is a Handler
    public static void Null()
    {
    }
}

class FunctionalHandlerExample
{
    [NotNull] readonly Handler _handler;

    // constructor elided...

    public void Run()
    {
        _handler();
    }
}