NetCore实现全局异常捕捉统一处理

做net项目时候，在Global.asax文件中可以通过Application_Error方法全局捕获异常并处理后统一跳转到自定义的错误页面。

下面是我个人在NetCore项目中实现全局捕获异常并统一处理的功能的记录，以便备份。

1、在项目根目录新建文件夹Filter，并在文件夹下新建类，命名为GlobalExceptionFilter.cs

using Microsoft.AspNetCore.Mvc.Filters;
using System;
using CMSCore.Web.Core;

namespace CMSCore.Web.Filter
{
    public class GlobalExceptionFilter : IExceptionFilter
    {
        public void OnException(ExceptionContext context)
        {
            Exception ex = context.Exception;
            Log4Net.Error("系统出错", ex);//记录错误日志
            context.ExceptionHandled = true; //代表异常已经处理，不会再跳转到开发调试时的异常信息页，可以跳转到我们下面自定义的方法中。若开发过程可以将
　　　　　　  该行注释掉，则直接抛出异常调试

            //通过HTTP请求头来判断是否为Ajax请求，Ajax请求的request headers里都会有一个key为x-requested-with，值“XMLHttpRequest”
            var requestData= context.HttpContext.Request.Headers.ContainsKey("x-requested-with"); 
            bool IsAjax = false;
            if (requestData)
            {
                IsAjax = context.HttpContext.Request.Headers["x-requested-with"] == "XMLHttpRequest" ? true :false;
            }
            if(!IsAjax)//不是异步请求则跳转页面，异步请求则返回json
            { 
                context.RouteData = new Microsoft.AspNetCore.Routing.RouteData();
                context.RouteData.Values.Add("controller", "home");
                context.RouteData.Values.Add("action", "error");
                context.Result = RedirectHelper.UrlFail(context.RouteData);
            }
            else  
                context.Result = RedirectHelper.JsonError();
           
        }
    }
}

2、RedirectHelper.cs的代码

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Routing;

namespace CMSCore.Web.Core
{

    public class RedirectHelper 
    {

        public static  AjaxModel AjaxModel(int code,string msg,dynamic data=null,string url=null)
        {
            return new AjaxModel()
            {
                Code=code,
                Msg=msg,
                Data=data,
                Url=url
            };
        }
        public static ActionResult JsonError()
        {
            JsonResult json = new JsonResult(AjaxModel(500, "系统出错啦"));
            return json;
        }

        public static ActionResult UrlFail(RouteData route)
        {
            RedirectToActionResult result = new RedirectToActionResult(route.Values["action"].ToString(), route.Values["controller"].ToString(), null);
            return result;
        }

    }

    /// <summary>
    /// Json返回结构
    /// </summary>
    public class AjaxModel
    {
        public int Code { get; set; }
        public string Msg { get; set; }
        public object Data { get; set; }
        public string Url { get; set; }
    }

}

3、在Startup.cs中，ConfigureServices方法添加该GlobalExceptionFilter为异常处理机制。

//记得引用对应命名空间
// This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
            //添加数据库操作上下文
            services.AddDbContext<BcmfDBContext>(option => option.UseSqlServer(Configuration.GetConnectionString("DefaultConnectionString")));
            //添加全局异常处理机制
            services.AddMvc(option=>{
                option.Filters.Add<GlobalExceptionFilter>();
            });
        }