在完成教程(专业ASP.NETMVC-Nerd晚餐)时，我遇到了这段代码:publicIEnumerableGetRuleViolations(){if(String.IsNullOrEmpty(Title))yieldreturnnewRuleViolation("Titlerequired","Title");if(String.IsNullOrEmpty(Description))yieldreturnnewRuleViolation("Descriptionrequired","Description");if(String.IsNullOrEmpty(HostedBy))yi