asp.net 组合模式的一个例子

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); 
} 
} 
}