public class CircusPerformer
 {
   public List<string> PlayedItem { get; private set; }
 
   public CircusPerformer()
   {
     PlayedItem=new List<string>();
   }
   public CircusPerformer StartShow()
   {
     //make a speech and start to show
     return this;
   }
   public CircusPerformer MonkeysPlay()
   {
     //monkeys do some show
     PlayedItem.Add("MonkeyPlay");
     return this;
   }
   public CircusPerformer ElephantsPlay()
   {
     //elephants do some show
     PlayedItem.Add("ElephantPlay");
     return this;
   }
   public CircusPerformer TogetherPlay()
   {
     //all of the animals do some show
     PlayedItem.Add("TogetherPlay");
     return this;
   }
   public void EndShow()
   {
     //finish the show
   }

[Test]
    public void All_shows_can_be_invoked_by_fluent_way()
    {
      //Arrange
      var circusPerformer = new CircusPerformer();
       
      //Act
      circusPerformer
        .MonkeysPlay()
        .ElephantsPlay()
        .StartShow()
        .TogetherPlay()
        .EndShow();
 
      //Assert
      circusPerformer.PlayedItem.Count.Should().Be(3);
      circusPerformer.PlayedItem.Contains("MonkeysPlay");
      circusPerformer.PlayedItem.Contains("ElephantsPlay");
      circusPerformer.PlayedItem.Contains("TogetherPlay");
    }

public abstract class Performer
 {
   public abstract ICircusPlayer CircusPlayer { get; }
   public abstract ICircusPlayer StartShow();
   public abstract void EndShow();
 }

public interface ICircusPlayer
{
  IList PlayedItem { get; }
  ICircusPlayer MonkeysPlay();
  ICircusPlayer ElephantsPlay();
  Performer TogetherPlay();
}

public class CircusPerformer:Performer
 {
   private ICircusPlayer _circusPlayer;
 
   override public ICircusPlayer CircusPlayer { get { return _circusPlayer; } }
 
   public override ICircusPlayer StartShow()
   {
     //make a speech and start to show
     _circusPlayer=new CircusPlayer(this);
     return _circusPlayer;
   }
   
   public override void EndShow()
   {
     //finish the show
   }
 }

var circusPerfomer = new CircusPerfomerWithGenericMethod();
      circusPerfomer.Show<Dog>(new Dog());
      circusPerfomer.Show(new Dog());

public class Drawing<TShape> where TShape :IShape
  {
    public TShape Shape { get; private set; }
    public TShape Draw(TShape shape)
    {
      //drawing this shape
      Shape = shape;
      return shape;
    }
  }

public void DrawPig(Circle head, Rectangle mouth)
   {
     _history.Clear();
     //use generic class, complier can not infer the correct type according to parameters
     Register(
       new Drawing<Circle>().Draw(head),
       new Drawing<Rectangle>().Draw(mouth)
       );
   }

public static class Drawer
 {
   public static Drawing<TShape> For<TShape>(TShape shape) where TShape:IShape
   {
     return new Drawing<TShape>();
   }
 }

public void DrawDog(Circle head, Rectangle mouth)
   {
     _history.Clear();
     //fluent implements
     Register(
       Drawer.For(head).Draw(head),
       Drawer.For(mouth).Draw(mouth)
     );
   }

xx.MapPath(
        Path.For(_student).Property(x => x.Name),
        Path.For(_student).Property(x => x.Email),
        Path.For(_customer).Property(x => x.Name),
        Path.For(_customer).Property(x => x.Email),
        Path.For(_manager).Property(x => x.Name),
        Path.For(_manager).Property(x => x.Email)
        )

public class Path<TModel>
 {
   private TModel _model;
   public Path(TModel model)
   {
     _model = model;
   }
   public PropertyItem<TValue> Property<TValue>(Expression<Func<TModel, TValue>> propertyExpression)
   {
     var item = new PropertyItem<TValue>(propertyExpression.PropertyName(), propertyExpression.PropertyValue(_model),_model);
     return item;
   }
 }

public static class Path
  {
    public static Path<TModel> For<TModel>(TModel model)
    {
      var path = new Path<TModel>(model);
      return path;
    }
  }

public Validator<TValue> MapPath(params PropertyItem<TValue>[] properties)
   {
     foreach (var propertyItem in properties)
     {
       _items.Add(propertyItem);
     }
     return this;
   }

[Test]
   public void Should_validate_model_values()
   {
 
     //Arrange
     var validator = new Validator<string>();
     validator.MapPath(
       Path.For(_student).Property(x => x.Name),
       Path.For(_student).Property(x => x.Email),
       Path.For(_customer).Property(x => x.Name),
       Path.For(_customer).Property(x => x.Email),
       Path.For(_manager).Property(x => x.Name),
       Path.For(_manager).Property(x => x.Email)
       )
      .OnCondition((model)=>!string.IsNullOrEmpty(model.ToString()));
      
     //Act
     validator.Validate();
 
     //Assert
     var result = validator.Result();
     result.Count.Should().Be(3);
     result.Any(x => x.ModelType == typeof(Student) && x.Name == "Email").Should().Be(true);
     result.Any(x => x.ModelType == typeof(Customer) && x.Name == "Name").Should().Be(true);
     result.Any(x => x.ModelType == typeof(Manager) && x.Name == "Email").Should().Be(true);
   }