using System;

​

public class Program

{

    public static void Main()

    {

        var theThingTrue = new BuilderFoo().BuildFooTrue()

            .WithSomePropertyOnlyForTrue("face").Build();

        //var theThingTrueCompilerError = new BuilderFoo().BuildFooTrue().WithB(5).Build(); // compiler error

        var theThingFalse = new BuilderFoo().BuildFooFalse()

            .WithB(5).Build();

        //var theThingFalseCompilerError = new BuilderFoo().BuildFooFalse().WithSomePropertyOnlyForTrue("face").Build(); // compiler error

        Console.WriteLine("hello");

    }

}

​

    public interface ISettings

    {

        string SomePropertyOnlyForTrue { get; }

        int B { get; }

    }

​

    public class Settings : ISettings

    {

        public string SomePropertyOnlyForTrue { get; }

        public int B { get; }

        public Settings(string somePropertyOnlyForTrue)

        {

            SomePropertyOnlyForTrue = somePropertyOnlyForTrue;

        }

        public Settings(int b)

        {

            B = b;

        }

    }

​

    public interface IBuilderFoo

    {

        IBuilderFooTrue BuildFooTrue();

        IBuilderFooFalse BuildFooFalse();

    }

​

    public class BuilderFoo : IBuilderFoo

    {

        public IBuilderFooTrue BuildFooTrue()

        {

            return new BuilderFooTrue();

        }

        public IBuilderFooFalse BuildFooFalse()

        {

            return new BuilderFooFalse();

        }

    }

​

    public interface IBuilderFooTrue

    {

        IBuilderFooTrue WithSomePropertyOnlyForTrue(string value);

        ISettings Build();

    }

​

    public class BuilderFooTrue : IBuilderFooTrue

    {

        private string _somePropertyOnlyForTrue = string.Empty;

        public IBuilderFooTrue WithSomePropertyOnlyForTrue(string value)

        {

            _somePropertyOnlyForTrue = value;

            return this;

        }

        public ISettings Build()

        {

            return new Settings(_somePropertyOnlyForTrue);

        }

    }

​

    public interface IBuilderFooFalse

    {

        IBuilderFooFalse WithB(int value);

        ISettings Build();

    }

​

    public class BuilderFooFalse : IBuilderFooFalse

    {

        private int _b;

        public IBuilderFooFalse WithB(int value)

        {

            _b = value;

            return this;

        }

        public ISettings Build()

        {

            return new Settings(_b);

        }

    }