假设如果我们要出国，当然要先递交申请给出国办事处，然后由中国办事处再转交给你想去的国家的大使馆，让他们审核你的信息。如果用工厂模式可以这么做。
1 
public abstract class Office
2 {
3 public abstract void CheckInfo();
4 }
5
6 public class USAoffice : Office
7 {
8 public override void CheckInfo()
9 { Console.WriteLine("This ia USAoffice CheckInfo"); }
10 }
11
12 public class UKoffice : Office
13 {
14 public override void CheckInfo()
15 { Console.WriteLine("This ia UKoffice CheckInfo"); }
16
17 }
18
19 public abstract class Creator
20 {
21 public abstract Office factory();
22 }
23
24 public class USAcreator : Creator
25 {
26 public override Office factory()
27 { return new USAoffice(); }
28 }
29
30 public class UKCreator : Creator
31 {
32 public override Office factory()
33 { return new UKoffice(); }
34 }
35
36 public class Client
37 {
38 public static void Main()
39 {
40 Creator c1 = new USAcreator();
41 Creator c2 = new UKCreator();
42
43 Office l1 = c1.factory();
44 Office l2 = c2.factory();
45
46 l1.CheckInfo();
47
48 Console.WriteLine("-----------------");
49
50 l2.CheckInfo();
51 }
52 }
public abstract class Office2
{3
public abstract void CheckInfo();4
} 5
6
public class USAoffice : Office7
{8
public override void CheckInfo()9
{ Console.WriteLine("This ia USAoffice CheckInfo"); }10
} 11
12
public class UKoffice : Office13
{14
public override void CheckInfo()15
{ Console.WriteLine("This ia UKoffice CheckInfo"); }16
17
} 18
19
public abstract class Creator20
{21
public abstract Office factory();22
} 23
24
public class USAcreator : Creator25
{26
public override Office factory()27
{ return new USAoffice(); }28
} 29
30
public class UKCreator : Creator31
{32
public override Office factory()33
{ return new UKoffice(); }34
} 35
36
public class Client37
{38
public static void Main()39
{40
Creator c1 = new USAcreator();41
Creator c2 = new UKCreator();42
43
Office l1 = c1.factory();44
Office l2 = c2.factory();45
46
l1.CheckInfo();47
48
Console.WriteLine("-----------------");49
50
l2.CheckInfo();51
}52
}
这是我参考吕老师的工厂模式的设计，他的文章写得很好，但这个设计并不能满足我的需求，因为这个模式在Client需要手动实例一个对象，如在Client端Creator c1 = new USAcreator();。所以我自己改良一下。
1
2 public abstract class Office
3 {
4 public abstract void CheckInfo();
5 }
6
7 public class USAoffice : Office
8 {
9 public override void CheckInfo()
10 { Console.WriteLine("This ia USAoffice CheckInfo"); }
11 }
12
13 public class UKoffice : Office
14 {
15 public override void CheckInfo()
16 { Console.WriteLine("This ia UKoffice CheckInfo"); }
17
18 }
19 public class Creator
20 {
21 public static Office Factory(string OfficeName)
22 {
23 if (OfficeName == "USA")
24 {
25 return new USAoffice();
26 }
27 if (OfficeName == "UK")
28 {
29 return new UKoffice();
30 }
31 }
32 }
33 public class Client
34 {
35 public static void Main()
36 {
37 string OfficeName = Console.ReadLine();
38 Office ConcreteOffice= Creator.Factory(OfficeName);
39
40 ConcreteOffice.CheckInfo();
41
42 }
43 }
2
public abstract class Office3
{4
public abstract void CheckInfo();5
} 6
7
public class USAoffice : Office8
{9
public override void CheckInfo()10
{ Console.WriteLine("This ia USAoffice CheckInfo"); }11
} 12
13
public class UKoffice : Office14
{15
public override void CheckInfo()16
{ Console.WriteLine("This ia UKoffice CheckInfo"); }17
18
} 19
public class Creator20
{21
public static Office Factory(string OfficeName)22
{23
if (OfficeName == "USA")24
{25
return new USAoffice();26
}27
if (OfficeName == "UK")28
{29
return new UKoffice();30
}31
}32
} 33
public class Client34
{35
public static void Main()36
{37
string OfficeName = Console.ReadLine();38
Office ConcreteOffice= Creator.Factory(OfficeName);39
40
ConcreteOffice.CheckInfo();41
42
}43
}
这个好处就在factory通过传递参数能自动判断该创建哪个实例，Client取到OfficeName就可以自动判断并创建所需要的实例。当然一眼也可以看出这个设计的致命点，就是如果以后Office越来越多，Creator的factory函数将会臃肿，不过目前这个设计足以满足我的需求啊。
第一次设计，虽然不好，但也能完成任务，以后发现问题再重构，一口并不能吃成胖子。