Asp.net Core过滤器

1. Asp.net Core五类过滤器：Authorization Filter、Resource Filter、Acton Filter、Exception Filter、Result Filter。优先级逐次递减。
2. 过滤器使用
   1. 　

      public class GlobalFiler: Attribute,IAuthorizationFilter
          {
              public void OnAuthorization(AuthorizationFilterContext context)
              {
                  context.Result = new JsonResult("全局权限设置");
              }
      
          }
      public class MyFilter : Attribute,IActionFilter,IOrderedFilter
          {
              public int Order { get; set; }
      
              public void OnActionExecuted(ActionExecutedContext context)
              {
              }
      
              public void OnActionExecuting(ActionExecutingContext context)
              {
              }
          }
      //ActionFilterAttribute继承了Attribute、IActionFilter、IOrderedFilter等
      public class MyFilter2 : ActionFilterAttribute
          {
      　　     public override void OnActionExecuting(ActionExecutingContext context)
              {
                  //如果失败，页面提示 
                  context.Result = new JsonResult("MyFilter2设置，无权限访问");
              }
          }

3. 过滤器注册，分为两种：全局注册和用Attribute区域注册，用在特定Action上。
   1. 全局注册Startup.cs

      public void ConfigureServices(IServiceCollection services)
              {
                  services.AddMvc(config => config.Filters.Add(new GlobalFiler()));
                  //services.AddMvc(config => config.Filters.Add(typeof(GlobalFiler)));
              }

   2. 区域注册

      [Route("api/[controller]")]
          [MyFilter(Order = )]
          public class ValuesController : Controller
          {
              // GET api/values
              [HttpGet]
              [MyFilter2(Order = )]
              public IEnumerable<string> Get()
              {
                  return new string[] { "value1", "value2" };
              }
          }

4. 过滤器执行顺序
   1. 默认执行顺序：全局过滤器优先于控制器过滤器，控制器过滤器优先于Action方法过滤器。　　
   2. 通过IOrderedFilter覆盖默认执行顺序，此接口公开Order属性表示优先级，Order值越小优先级越高。

　　参考文档：https://www.cnblogs.com/tdfblog/p/filters-in-aspnet-core-mvc.html