设计模式-规约模式C#版

using System; using System.Collections.Generic; using System.Linq; using System.Text;  namespace DomainModel.Model {     /// <summary>     /// 规约模式     /// </summary>     /// <typeparam name="T"></typeparam>     public interface ISpecification<T>     {         bool IsSatisfiedBy(T entity);         /// <summary>         /// 与规约         /// </summary>         /// <param name="specification"></param>         /// <returns></returns>         ISpecification<T> And(ISpecification<T> specification);         /// <summary>         /// 或规约         /// </summary>         /// <param name="specification"></param>         /// <returns></returns>         ISpecification<T> Or(ISpecification<T> specification);         /// <summary>         /// 非规约         /// </summary>         /// <returns></returns>         ISpecification<T> Not();     }      public class Customer     {         private ISpecification<Customer> _hasReachedMax;         private ISpecification<Customer> _active;          public Customer(ISpecification<Customer> hasReachedMax, ISpecification<Customer> active)         {             this._hasReachedMax = hasReachedMax;             this._active = active;         }         public int TotalRentNumber { get; set; }         public bool Active         {             get { return true; }         }          public bool CanRent()         {             var specification = this._hasReachedMax.Not().And(this._active.Not());             return specification.IsSatisfiedBy(this);         }     }      public class HasReachedMaxSpecification : CompositeSpecification<Customer>     {         public override bool IsSatisfiedBy(Customer entity)         {             return entity.TotalRentNumber >= 6;         }     }     public class CustomerActiveSpecification : CompositeSpecification<Customer>     {         public override bool IsSatisfiedBy(Customer entity)         {             return entity.Active;         }     }     /// <summary>     /// 组合规约     /// </summary>     /// <typeparam name="T"></typeparam>     public abstract class CompositeSpecification<T> : ISpecification<T>     {          public abstract bool IsSatisfiedBy(T entity);          public ISpecification<T> And(ISpecification<T> specification)         {             return new AndSpecification<T>(this, specification);         }          public ISpecification<T> Not()         {             return new NotSpecification<T>(this);         }          public ISpecification<T> Or(ISpecification<T> specification)         {             throw new NotImplementedException();         }       }      public class AndSpecification<T> : CompositeSpecification<T>     {         private ISpecification<T> _left;         private ISpecification<T> _right;         public AndSpecification(ISpecification<T> left, ISpecification<T> right)         {             this._left = left;             this._right = right;         }         public override bool IsSatisfiedBy(T entity)         {             return this._left.IsSatisfiedBy(entity) && this._right.IsSatisfiedBy(entity);         }     }      public class OrSpecification<T> : CompositeSpecification<T>     {         private ISpecification<T> _left;         private ISpecification<T> _right;         public OrSpecification(ISpecification<T> left, ISpecification<T> right)         {             this._left = left;             this._right = right;         }         public override bool IsSatisfiedBy(T entity)         {             return this._left.IsSatisfiedBy(entity) || this._right.IsSatisfiedBy(entity);         }     }      public class NotSpecification<T> : CompositeSpecification<T>     {         private ISpecification<T> _inner;         public NotSpecification(ISpecification<T> inner)         {             this._inner = inner;         }         public override bool IsSatisfiedBy(T entity)         {             return !this._inner.IsSatisfiedBy(entity);         }     } }