asp.net core3.1 实战开发（Filter的使用）

.net core 异常过滤器的使用

首先代码如下

public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
    #region Identity
    private readonly ILogger<CustomExceptionFilterAttribute> _logger;
    private readonly IModelMetadataProvider _modelMetadataProvider;
    public CustomExceptionFilterAttribute(ILogger<CustomExceptionFilterAttribute> logger
        , IModelMetadataProvider modelMetadataProvider)
    {
        this._modelMetadataProvider = modelMetadataProvider;
        this._logger = logger;
    }
    #endregion
    /// <summary>
    /// 异常发生，但是没有处理时
    /// 异常之后得写日志
    /// </summary>
    /// <param name="context"></param>
    public override void OnException(ExceptionContext context)
    {
        if (!context.ExceptionHandled)
        {
            this._logger.LogError($"{context.HttpContext.Request.RouteValues["controller"]} is Error");
            if (this.IsAjaxRequest(context.HttpContext.Request))//header看看是不是XMLHttpRequest
            {
                context.Result = new JsonResult(new
                {
                    Result = false,
                    Msg = context.Exception.Message
                });//中断式---请求到这里结束了，不再继续Action
            }
            else
            {
                var result = new ViewResult { ViewName = "~/Views/Shared/Error.cshtml" };
                result.ViewData = new ViewDataDictionary(_modelMetadataProvider, context.ModelState);
                result.ViewData.Add("Exception", context.Exception);
                context.Result = result;
            }
            context.ExceptionHandled = true;
        }
    }
    private bool IsAjaxRequest(HttpRequest request)
    {
        string header = request.Headers["X-Requested-With"];
        return "XMLHttpRequest".Equals(header);
    }
}

第一种使用方式

[ServiceFilter(typeof(CustomExceptionFilterAttribute))]
public IActionResult Index()
{
    return View();
}

 public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped(typeof(CustomExceptionFilterAttribute));//不是直接new  而是容器生成 就可以自动注入了
}

第二种使用方式

[TypeFilter(typeof(CustomExceptionFilterAttribute))]
public IActionResult Index()
{
    return View();
}

第三种使用方式

自定义实现

 /// <summary>
    /// 基于完成Filter的依赖注入
    /// </summary>
    public class CustomIOCFilterFactoryAttribute : Attribute, IFilterFactory
    {
        private readonly Type _FilterType = null;

        public CustomIOCFilterFactoryAttribute(Type type)
        {
            this._FilterType = type;
        }
        public bool IsReusable => true;

        public IFilterMetadata CreateInstance(IServiceProvider serviceProvider)
        {
            //return (IFilterMetadata)serviceProvider.GetService(typeof(CustomExceptionFilterAttribute));

            return (IFilterMetadata)serviceProvider.GetService(this._FilterType);
        }
    }

使用

[CustomIOCFilterFactoryAttribute(typeof(CustomExceptionFilterAttribute))]/
public IActionResult Index()
{
    return View();
}

.net core 行为过滤器的使用

public class CustomActionFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext context)
        {
        //告诉浏览器缓存（新开页面，刷新并不会），浏览器不同会有不同效果
        context.HttpContext.Response.Headers.Add("Cache-Control", "public,max-age=6000");
            Console.WriteLine($"This {nameof(CustomActionFilterAttribute)} OnActionExecuted{this.Order}");
        }
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomActionFilterAttribute)} OnActionExecuting{this.Order}");
        }
        public override void OnResultExecuting(ResultExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomActionFilterAttribute)} OnResultExecuting{this.Order}");
        }
        public override void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine($"This {nameof(CustomActionFilterAttribute)} OnResultExecuted{this.Order}");
        }
    }

    public class CustomControllerFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext context)
        {
            Console.WriteLine($"This {nameof(CustomControllerFilterAttribute)} OnActionExecuted {this.Order}");
        }
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomControllerFilterAttribute)} OnActionExecuting{this.Order}");
        }
        public override void OnResultExecuting(ResultExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomControllerFilterAttribute)} OnResultExecuting{this.Order}");
        }
        public override void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine($"This {nameof(CustomControllerFilterAttribute)} OnResultExecuted{this.Order}");
        }
    }

    public class CustomGlobalFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext context)
        {
            Console.WriteLine($"This {nameof(CustomGlobalFilterAttribute)} OnActionExecuted{this.Order}");
        }
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomGlobalFilterAttribute)} OnActionExecuting{this.Order}");
        }
        public override void OnResultExecuting(ResultExecutingContext context)
        {
            Console.WriteLine($"This {nameof(CustomGlobalFilterAttribute)} OnResultExecuting{this.Order}");
        }
        public override void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine($"This {nameof(CustomGlobalFilterAttribute)} OnResultExecuted{this.Order}");
        }
    }

/// <summary>
/// 全局---控制器---Action  Order默认0，从小到大执行  可以负数
 /// </summary>
 /// <returns></returns>
 [CustomActionFilterAttribute(Order = 10)]
 [CustomActionFilterAttribute]
 [CustomActionCacheFilterAttribute(Order = -1)]
 public IActionResult Info()
 {
     Console.WriteLine($"This is {nameof(ThirdController)} Info");

     base.ViewBag.Now = DateTime.Now;
     Thread.Sleep(2000);
     return View();
 }

.net core Resource过滤器的使用（避免行为再次执行直接返回视图）

// <summary>
    /// 
    /// </summary>
    public class CustomResourceFilterAttribute : Attribute, IResourceFilter, IFilterMetadata
    {
        private static Dictionary<string, IActionResult> CustomCache = new Dictionary<string, IActionResult>();
        /// <summary>
        /// 发生在其他动作之前
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuting(ResourceExecutingContext context)
        {
            Console.WriteLine($"This is {nameof(CustomResourceFilterAttribute) }OnResourceExecuting");
            //if 有缓存，直接返回缓存
            string key = context.HttpContext.Request.Path;
            if (CustomCache.ContainsKey(key))
            {
                context.Result = CustomCache[key];//断路器--到Result生成了，但是Result还需要转换成Html
            }
        }
        /// <summary>
        /// 发生在其他动作之后
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuted(ResourceExecutedContext context)
        {
            Console.WriteLine($"This is {nameof(CustomResourceFilterAttribute) }OnResourceExecuted");
            //这个应该缓存起来
            string key = context.HttpContext.Request.Path;
            if (!CustomCache.ContainsKey(key))
            {
                CustomCache.Add(key, context.Result);
            }
        }
    }

[CustomResourceFilterAttribute]//缓存了变量
 public IActionResult Info()
 {
     Console.WriteLine($"This is {nameof(ThirdController)} Info");

     base.ViewBag.Now = DateTime.Now;
     Thread.Sleep(2000);
     return View();
 }

全局生效

public void ConfigureServices(IServiceCollection services)
        {
            services.AddSession();
            services.AddControllersWithViews(
                options =>
                {
                    options.Filters.Add<CustomExceptionFilterAttribute>();//全局注册
                    options.Filters.Add<CustomGlobalFilterAttribute>();
                });
        }