【C# ValueTypes】
1、哪些类型是ValueType？
The value types consist of two main categories:
Structs fall into these categories:
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Numeric types
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User defined structs.
2、内置C#值类型实际是C#内置类的alias。例如：
3、The C# type keywords and their aliases are interchangeable.
4、以下2种初始化的是，一个会调用构造函数初始化，一个不会。
int myInt;
myInt = new int(); // Invoke default constructor for int type.
5、Data types are separated into value types and reference types. Value types are either stack-allocated or allocated inline in a structure. Reference types are heap-allocated. Both reference and value types are derived from the ultimate base class Object. In cases where it is necessary for a value type to behave like an object, a wrapper that makes the value type look like a reference object is allocated on the heap, and the value type's value is copied into it. The wrapper is marked so the system knows that it contains a value type. This process is known as boxing, and the reverse process is known as unboxing. Boxing and unboxing allow any type to be treated as an object.
Although ValueType is the implicit base class for value types, you cannot create a class that inherits from ValueType directly. Instead, individual compilers provide a language keyword or construct (such as struct in C# and Structure…End Structure in Visual Basic) to support the creation of value types.
参考：
1、http://msdn.microsoft.com/zh-cn/library/ya5y69ds.aspx
2、http://msdn.microsoft.com/zh-cn/library/s1ax56ch.aspx
3、http://msdn.microsoft.com/zh-cn/library/system.valuetype(v=vs.110).aspx
