1.typeof
请看代码:
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typeof一般用在反射里,这里例子使用反射分别获得一个自定义类型的名字,方法和所有成员。比较简单,就不多解释了。
2.sizeof
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要使用sizeof操作符,就必须把代码标记为unsafe,编译的时候,开启unsafe开关。
程序结果为:
一些基本类型的大小
sizeof short = 2
sizeof int = 4
sizeof long = 8
sizeof bool = 1
那么我们想要测试自己定义的值类型(比如说结构)呢?
请看如下代码:
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如果不编译,你会认为输出什么?你大概会认为,第一个结构没有成员,那就是0,第二个结构是15(你可以看上一个例子里输出的数值),第三个结构是0+15=15。
很可惜,你错了。
输出结果为:
sizeof StructWithNoMembers structure = 1
sizeof StructWithMembers structure = 16
sizeof CompositeStruct structure = 20
为什么会这样呢?这是由填充和结构对齐造成的,这与编译器在输出文件的映像中如何布置结构有关。例如,如果一个结构有3个字节长,而字节对齐会被设置成4字节,那么编译器自动填充一个额外的字节,sizeof报告这个结构有4字节。
/* 说明:原书《Inside C# 2rd》在说明的时候有误,因为它的例子里是这样的:
struct CompositeStruct
{
StructWithNoMembers a;
StructWithMembers b;
StructWithNoMembers c;
}
而在后面的说明中却以
struct CompositeStruct
{
StructWithNoMembers a;
StructWithMembers b;
}
说明的。而输出结果却又是
struct CompositeStruct
{
StructWithNoMembers a;
StructWithMembers b;
StructWithNoMembers c;
}
的结果。不过没有大碍,大家看书的时候注意一下吧。
此文参考:《C# 技术解密》