.net mvc及WebApi中拦截器、过滤器的用法；在拦截器中获取api参数的值，进行预处理。

一、.net mvc中使用拦截器

引用using System.Web.Mvc;

继承 : ActionFilterAttribute,IActionFilter

public void OnAuthorization(AuthorizationContext filterContext)
{
                
}

获得Action中参数的值，提前进行预处理

        private string GetPara(ActionExecutingContext filterContext, string ParaName)
        {
            if (filterContext.HttpContext.Request.Params.AllKeys.Contains(ParaName))
            {
                return filterContext.HttpContext.Request.Params[ParaName];
            }
            return string.Empty;
        }

二、WebApi中使用拦截器

引用using System.Web.Http.Filters;

继承: ActionFilterAttribute

        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            //base.OnActionExecuting(actionContext);
        }

已WebApi为例编写一个拦截器：

    public class MyFilterTest : ActionFilterAttribute
    {
        string _input = string.Empty;
        public MyFilterTest(string input)
        {
            _input = input;
        }

        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            string paramValue = GetParaFromRequest(actionContext.Request, _input);
            if (paramValue == "Data111")
            {
                actionContext.Response = new HttpResponseMessage(System.Net.HttpStatusCode.OK);
                actionContext.Response.Content = new ObjectContent(typeof(string), "Data111", new JsonMediaTypeFormatter());
                return;
            }
            //base.OnActionExecuting(actionContext);
        }

        /// 

        /// 从请求中获取参数
        /// 
        /// 
        /// 
        /// 
        public static string GetParaFromRequest(HttpRequestMessage request, string ParaKey)
        {
            try
            {
                foreach (var item in request.GetQueryNameValuePairs())
                {
                    if (item.Key == ParaKey)
                    {
                        return item.Value.ToString();
                    }
                }

                return string.Empty;
            }
            catch (Exception ex)
            {
                return string.Empty;
            }
        }
    }

调用：

        [HttpGet]
        [MyFilterTest(input: "inputParam")]
        public string Date2(string inputParam)
        {
            return "hahaha2222:【" + inputParam + "】" + DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss");
        }

结果：调用Data2接口是，inputParam传入非"Data111"时，按接口内部返回值返回。当inputParam传入“Data111”时，在拦截器中直接返回了Data111，响应结束，不进入Data2接口中。