泛型约束的大概模样

 

                                where T:struct                                     使用结构约束，类型T必须是值类型

                                where T:calss                                       类约束指定，类型T必须是引用类型

                                where T:IFoo                                            指定类型T必须执行结构IFoo

                                where T:Foo                                            指定类型T必须派生于基类Foo

                               where T:new()                                       指定类型T必须有一个默认构造函数 

                                 where T:U                                          类型T派生于泛型类型V（裸类型约束）