Filter 过滤器

1.Action前和Action后

IActionFilter（还须要继承特性）

   /// <summary>
    /// Action的Filter`
    /// </summary>
    public class CustomActionFilterAttribute : Attribute, IActionFilter
    {
        private ILogger<CustomActionFilterAttribute> _logger = null;
        public CustomActionFilterAttribute(ILogger<CustomActionFilterAttribute> logger)
        {
            this._logger = logger;
        } 
        public void OnActionExecuted(ActionExecutedContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executed!");
            Console.WriteLine("ActionFilter Executed!");
            //this._logger.LogDebug("ActionFilter Executed!");
        } 
        public void OnActionExecuting(ActionExecutingContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executing!");
            Console.WriteLine("ActionFilter Executing!");
            //this._logger.LogDebug("ActionFilter Executing!");
        }
    }

    /// <summary>
    /// 标记到Controller
    /// </summary>
    public class CustomControllerActionFilterAttribute : Attribute, IActionFilter
    {
        private ILogger<CustomControllerActionFilterAttribute> _logger = null;
        public CustomControllerActionFilterAttribute(ILogger<CustomControllerActionFilterAttribute> logger)
        {
            this._logger = logger;
        }
        public void OnActionExecuted(ActionExecutedContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executed!");
            Console.WriteLine("ActionFilter Executed!");
            //this._logger.LogDebug("ActionFilter Executed!");
        }
        public void OnActionExecuting(ActionExecutingContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executing!");
            Console.WriteLine("ActionFilter Executing!");
            //this._logger.LogDebug("ActionFilter Executing!");
        }
    }

2. 异常处理的Filter

ExceptionFilterAttribute

/// <summary>
/// 异常处理的Filter
/// </summary>
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
private readonly IHostingEnvironment _hostingEnvironment;
private readonly IModelMetadataProvider _modelMetadataProvider;
//private Logger logger = Logger.CreateLogger(typeof(CustomExceptionFilterAttribute));

/// <summary>
/// ioc来的
/// </summary>
/// <param name="hostingEnvironment"></param>
/// <param name="modelMetadataProvider"></param>
public CustomExceptionFilterAttribute(
IHostingEnvironment hostingEnvironment,
IModelMetadataProvider modelMetadataProvider)
{
_hostingEnvironment = hostingEnvironment;
_modelMetadataProvider = modelMetadataProvider;
}

/// <summary>
/// 没有处理的异常，就会进来
/// </summary>
/// <param name="filterContext"></param>
public override void OnException(ExceptionContext filterContext)
{
if (!filterContext.ExceptionHandled)//异常有没有被处理过
{
string controllerName = (string)filterContext.RouteData.Values["controller"];
string actionName = (string)filterContext.RouteData.Values["action"];
string msgTemplate = "在执行 controller[{0}] 的 action[{1}] 时产生异常";
//logger.Error(string.Format(msgTemplate, controllerName, actionName), filterContext.Exception);
if (this.IsAjaxRequest(filterContext.HttpContext.Request))//检查请求头
{
filterContext.Result = new JsonResult(
new
{
Result = false,
PromptMsg = "系统出现异常，请联系管理员",
DebugMessage = filterContext.Exception.Message
}//这个就是返回的结果
);
}
else
{
var result = new ViewResult { ViewName = "~/Views/Shared/Error.cshtml" };
result.ViewData = new ViewDataDictionary(_modelMetadataProvider, filterContext.ModelState);
result.ViewData.Add("Exception", filterContext.Exception);
filterContext.Result = result;
}
filterContext.ExceptionHandled = true;
}
}


private bool IsAjaxRequest(HttpRequest request)
{
string header = request.Headers["X-Requested-With"];
return "XMLHttpRequest".Equals(header);
}
}

3.请求页面前，没有进控制器

IResourceFilter

  /// <summary>
    /// 自定义的资源Filter
    /// </summary>
    public class CustomResourceFilterAttribute : Attribute, IResourceFilter
    {
        private static readonly Dictionary<string, object> _Cache = new Dictionary<string, object>();
        private string _cacheKey;
        /// <summary>
        /// 控制器实例化之前
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuting(ResourceExecutingContext context)
        {
            _cacheKey = context.HttpContext.Request.Path.ToString();
            if (_Cache.ContainsKey(_cacheKey))
            {
                var cachedValue = _Cache[_cacheKey] as ViewResult;
                if (cachedValue != null)
                {
                    context.Result = cachedValue;//  短路器   
                }
            }
        }
        /// <summary>
        /// 把请求都处理完的
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuted(ResourceExecutedContext context)
        {
            if (!String.IsNullOrEmpty(_cacheKey) &&
                !_Cache.ContainsKey(_cacheKey))
            {
                var result = context.Result as ViewResult;
                if (result != null)
                {
                    _Cache.Add(_cacheKey, result);
                }
            }
        }
    }

4.返回结果

IResultFilter

 /// <summary>
    /// Result的Filter
    /// </summary>
    public class CustomResultFilterAttribute : Attribute, IResultFilter
    {
        //private Logger logger = Logger.CreateLogger(typeof(CustomResultFilterAttribute));
        public void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine("OnResultExecuted Executed!");
            //logger.Info("OnResultExecuted Executed!");
        }

        public void OnResultExecuting(ResultExecutingContext context)
        {
            Console.WriteLine("OnResultExecuting Executing!");
            //logger.Info("OnResultExecuting Executing!");
        }
    }