using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Test { class Program { static void Main(string[] args) { var customer = new Customer { IsActive = true, LateFees = 100M, TotalRentNumber = 10 }; Console.WriteLine(customer.CanRent()); Console.ReadKey(); } } public interface ISpecification<T> { /// <summary> /// 是否可以租赁 /// </summary> bool IsSatisfiedBy(T entity); /// <summary> /// 与操作 /// </summary> ISpecification<T> And(ISpecification<T> other); /// <summary> /// 否操作 /// </summary> ISpecification<T> Not(); } /// <summary> /// 基类 /// </summary> public abstract class CompositeSpecification<T> : ISpecification<T> { public abstract bool IsSatisfiedBy(T candidate); public ISpecification<T> And(ISpecification<T> other) { return new AndSpecification<T>(this, other); } public ISpecification<T> Not() { return new NotSpecification<T>(this); } } /// <summary> /// 与操作 /// </summary> public class AndSpecification<T> : CompositeSpecification<T> { private ISpecification<T> leftSpecification; private ISpecification<T> rightSpecification; public AndSpecification(ISpecification<T> leftSpecification, ISpecification<T> rightSpecification) { this.leftSpecification = leftSpecification; this.rightSpecification = rightSpecification; } public override bool IsSatisfiedBy(T entity) { return leftSpecification.IsSatisfiedBy(entity) && rightSpecification.IsSatisfiedBy(entity); } } ///<summary> ///否操作 /// </summary> public class NotSpecification<T> : CompositeSpecification<T> { private ISpecification<T> innerSpecification; public NotSpecification(ISpecification<T> innerSpecification) { this.innerSpecification = innerSpecification; } public override bool IsSatisfiedBy(T entity) { return !innerSpecification.IsSatisfiedBy(entity); } } /// <summary> /// 是否达到最大的规定租赁数 /// </summary> public class HasReachedMaxSpecification : CompositeSpecification<Customer> { public override bool IsSatisfiedBy(Customer entity) { return entity.TotalRentNumber > 5; } } /// <summary> /// 是否激活 /// </summary> public class CustomerActiveSpecification : CompositeSpecification<Customer> { public override bool IsSatisfiedBy(Customer entity) { return entity.IsActive; } } /// <summary> /// 是否欠费 /// </summary> public class CustomerHasLateFeesSpecification : CompositeSpecification<Customer> { public override bool IsSatisfiedBy(Customer entity) { return entity.LateFees > 0; } } public class Customer { private ISpecification<Customer> hasReachedRentalThreshold; private ISpecification<Customer> customerIsActive; private ISpecification<Customer> customerHasLateFees; public Customer() { hasReachedRentalThreshold = new HasReachedMaxSpecification(); customerIsActive = new CustomerActiveSpecification(); customerHasLateFees = new CustomerHasLateFeesSpecification(); } /// <summary> /// 用户租赁DVD数量 /// </summary> public int TotalRentNumber { get; set; } /// <summary> /// 账户是否激活 /// </summary> public bool IsActive { get; set; } /// <summary> /// 用户之前是否还欠费 /// </summary> public decimal LateFees { get; set; } public bool CanRent() { ISpecification<Customer> canRent = customerIsActive.And(hasReachedRentalThreshold.Not()).And(customerHasLateFees.Not()); return canRent.IsSatisfiedBy(this); } } }