ASP.Net Core 6.0--ExceptionFilter和ActionFilter代码片段

Asp.Net Core中Filter大概有五种类型，分别为：authorization filter, resource filter, action filter, exception filter and result filter.

并且所有的filter一般都有同步版本和异步版本：IActionFilter, IAsyncActionFilter

这些filter有什么作用呢：ExceptionFilter可以让程序在发生exception时执行的代码，同样ActionFilter就是程序在执行Controller下面Action的时候执行的代码。比如在执行action之前统一做一下判断。

这里记录ExceptionFilter 和ActionFilter的简单代码片段:

MyExceptionFilter.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;

namespace WebApi
{
    public class MyExceptionFilter : IAsyncExceptionFilter
    {
        public Task OnExceptionAsync(ExceptionContext context)
        {
            context.Result = new ObjectResult(new { code = 500, message = "Error" });
            return Task.CompletedTask;
        }
    }
}

MyActionFilter.cs

using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.Filters;

namespace WebApi
{
    public class MyActionFilter : IAsyncActionFilter
    {
        public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
        {
            Console.WriteLine("before execute");
            // ControllerActionDescriptor ctrActionDes = context.ActionDescriptor as ControllerActionDescriptor; get some infomation in filter.
            ActionExecutedContext r = await next();
            if (r.Exception == null)
            {
                Console.WriteLine("no exception");
            }
            else
            {
                Console.WriteLine("Exception occur");
            }
        }
    }
}

然后在Program.cs文件里注册对应的filter:

builder.Services.Configure<MvcOptions>(options =>
{
    options.Filters.Add<MyExceptionFilter>();
});

builder.Services.Configure<MvcOptions>(opt =>
{
    opt.Filters.Add<MyActionFilter>();
});

完整的Program.cs文件：

using Microsoft.AspNetCore.Mvc;

namespace WebApi
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var builder = WebApplication.CreateBuilder(args);

            // Add services to the container.

            builder.Services.AddControllers();
            // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
            builder.Services.AddEndpointsApiExplorer();
            builder.Services.AddSwaggerGen();
            builder.Services.Configure<MvcOptions>(options =>
            {
                options.Filters.Add<MyExceptionFilter>();
            });

            builder.Services.Configure<MvcOptions>(opt =>
            {
                opt.Filters.Add<MyActionFilter>();
            });
            var app = builder.Build();

            // Configure the HTTP request pipeline.
            if (app.Environment.IsDevelopment())
            {
                app.UseSwagger();
                app.UseSwaggerUI();
            }

            app.UseHttpsRedirection();

            app.UseAuthorization();


            app.MapControllers();

            app.Run();
        }
    }
}