C#泛型

使用泛型的好处

type safety, 

所有类型相同, 减少编译报错

no casting, 

无需转换, 降低性能开销

no boxing and unboxing.

可以避免装箱拆箱, 减低性能消耗

泛型约束

ConstraintDescriptionwhere T : <name of interface>The type argument must be, or implement, the specified interface.where T : <name of base class>The type argument must be, or derive from, the specified classwhere T : UThe type argument must be, or derive from, the supplied type argument Uwhere T : new()The type argument must have a public default constructorwhere T : structThe type argument must be a value typewhere T : classThe type argument must be a reference type