ASP MVC过滤器，在哪里实现接口？

Question

只是想知道如何在 asp mvc 4 中使用过滤器。我发现有些人是这样定义它们的：

public class CustomFilter : ActionFilterAttribute

还有一些是这样的：

public class CustomFilter : ActionFilterAttribute, IActionFilter

ActionFilterAttribute 已经有所有操作需要重写，为什么还要实现接口呢？

同样例如在下一个代码中，最后再次调用过滤器，这是为什么呢？

public class 

CustomActionFilter : ActionFilterAttribute, IActionFilter
{
    void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext)


    {
        // TODO: Add your acction filter's tasks here

        // Log Action Filter Call
        MusicStoreEntities storeDB = new MusicStoreEntities();

        ActionLog log = new ActionLog()
        {
            Controller = filterContext.ActionDescriptor.ControllerDescriptor.ControllerName,
            Action = filterContext.ActionDescriptor.ActionName + " (Logged By: Custom 

Action Filter)",
            IP = filterContext.HttpContext.Request.UserHostAddress,
            DateTime = filterContext.HttpContext.Timestamp
        };

        storeDB.ActionLogs.Add(log);
        storeDB.SaveChanges();

        this.OnActionExecuting(filterContext);
    }
}

Answer 1

如果您检查MSDN definition of ActionFilterAttribute ，您会看到它是一个抽象类，继承了接口IActionFilter AND IResultFilter。

实际上继承自ActionFilterAttribute，

public class CustomFilter : ActionFilterAttribute

相当于继承类FilterAttribute和接口IActionFilter和IResultFilter

public class CustomFilter : FilterAttribute, IActionFilter, IResultFilter

和没有什么不同

public class CustomFilter : ActionFilterAttribute, IActionFilter, IResultFilter

所以从 ActionFilterAttribute 继承与从 ActionFilterAttribute 和 IActionFilter 继承没有什么不同。