[.Net Tips]Static
我们都知道静态变量属于类型之间共享的数据，但是自己也没有进去看看，近日有兴趣，写那些长篇大论似乎不在状态，时间紧迫，拿起static开始.
从代码开始
1: using System;
2: using System.Collections.Generic;
3: using System.Linq;
4: using System.Text;
5:
6: namespace StaticInstance
7: {
8:
9: class Program
10: {
11: static void Main(string[] args)
12: {
13: Test();
14: Console.Read();
15: }
16:
17: public static unsafe void Test()
18: {
19: fixed (char* address = BaseInstance.SharedVariable)
20: {
21: IntPtr i = new IntPtr(address);
22: Console.WriteLine("The Address Of BaseInstance.SharedVariable: {0}", i);
23: }
24:
25: fixed (char* address = BaseInstance.SharedVariable)
26: {
27: IntPtr i = new IntPtr(address);
28: Console.WriteLine("The Address Of BaseInstance.SharedVariable 2: {0}", i);
29: }
30:
31: fixed (char* address = InstanceA.SharedVariable)
32: {
33: IntPtr i = new IntPtr(address);
34: Console.WriteLine("The Address Of InstanceA.SharedVariable: {0}", i);
35: }
36:
37: fixed (char* address = InstanceB.SharedVariable)
38: {
39: IntPtr i = new IntPtr(address);
40: Console.WriteLine("The Address Of InstanceB.SharedVariable: {0}", i);
41: }
42: }
43: }
44:
45: public class BaseInstance
46: {
47: public static string SharedVariable = "This is the SharedVariable";
48: }
49:
50: public class InstanceA : BaseInstance
51: {
52:
53: }
54:
55: public class InstanceB : BaseInstance
56: {
57:
58: }
59: }
输出结果
可以看到各个类型之间共享了这一块内存。然而在原理上如何实现的呢?
小生斗胆猜测一下，日后有错再改了 :)
线索:
1. 在编译产生的元数据中存在.data区块，专门存放共享的数据
2. 类型在元数据中的布局指向的是元数据中的区块，在C++里ms我们可以这样表示
#program data_seg("BaseInstance")
string SharedVariable = "This is the sharedVariable"
#program restore
参考: http://msdn.microsoft.com/en-us/library/h90dkhs0(VS.80).aspx
这样应用程序在执行时，会为元数据中的数据分配空间，而类型上所制定的引用则是指向这块共享区域里的空间. 而类之间关系的继承，则应该还是按照继承的原则全部COPY父类的布局
这样，也就只会共享一块内存了
而关于静态方法.下面是ECMA的描述
Static methods are methods that are associated with a type, not with its instances.
个人觉得和静态变量的实现类似，然而没有去看源代码，不敢乱下结论。
