This is referred to as multicasting . to add an extra method to the delegate s list of methodsthe invocation listsimply requires adding two delegates using the addition or addition assignment operators or 若要向委托的方法列表(调用列表)中添加额外的方法,只需使用加法运算符或加法赋值运算符( “ + ”或“ + = ” )添加两个委托。