Both the casting and the boxing and unboxing operations degrade performance; the effect of boxing and unboxing can be quite significant in scenarios where you must iterate over large collections.

• 强制转换以及装箱和取消装箱操作都会降低性能;在必须对大型集合进行循环访问的情况下,装箱和取消装箱的影响非常明显。