CoreApi 3.1

一、过滤器方式

先定义一个异常过滤器

    /// <summary>
    /// 异常过滤器
    /// </summary>
    public class ExceptionFilter : IExceptionFilter
    {
        /// <summary>
        /// 发生异常时进入
        /// </summary>
        /// <param name="context"></param>
        public void OnException(ExceptionContext context)
        {
            if (context.ExceptionHandled == false)
            {
                context.Result = new ContentResult
                {
                    Content = context.Exception.Message,//这里是把异常输出，也可以不输出，也可以输出JSON结构的字符串。
                    StatusCode = StatusCodes.Status200OK,
                    ContentType = "text/html;charset=utf-8"
                };
            }
            context.ExceptionHandled = true;

            //写入日志，或者其它操作
            
        }
    }

再API控制器使用过滤器

[TypeFilter(typeof(ExceptionFilter))]//这里使用自定义过滤器
[ApiController]
public class MyController:ControllerBase
{
    //.....          
}

二、配置方式

在 Startup.cs 中的， Configure 配置中

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //异常配置文件写法
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler(config =>
                {
                    config.Run(async context =>
                    {
                        context.Response.StatusCode = 500;
                        context.Response.ContentType = "application/json";

                        var error = context.Features.Get<IExceptionHandlerFeature>();
                        if (error != null)
                        {
                            var ex = error.Error;

                            //输出异常内容，也可以不输出，也可以输出JSON结构的字符串
                            await context.Response.WriteAsync(ex.Message);
                        }
                    });
                });
            }
        }

三、中间件方式

先定义一个异常中间件

    public class CustomExceptionMiddleware
    {
        private readonly RequestDelegate _next;
        //private readonly ILogger<CustomExceptionMiddleware> _logger;
        public CustomExceptionMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext httpContext)
        {
            try
            {
                await _next(httpContext);
            }
            catch (Exception ex)
            {
                //写入日志或者其它操作
                //log
                await HandleExceptionAsync(httpContext, ex);
            }
        }

        private async Task HandleExceptionAsync(HttpContext httpContext, Exception ex)
        {
            httpContext.Response.StatusCode = StatusCodes.Status200OK;
            httpContext.Response.ContentType = "application/json;charset=utf-8";
            //输出异常内容
            await httpContext.Response.WriteAsync(ex.Message);
            //如果不输出，则需要下面这句
            //return Task.CompletedTask;
        }
    }

 再定义一个扩展类

    public static class CustomExceptionMiddlewareExtensions
    {
        public static IApplicationBuilder UseCustomExceptionMiddleware(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<CustomExceptionMiddleware>();
        }
    }

在 Startup 的 Configure 中配置

            //异常配置文件写法
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseCustomExceptionMiddleware();
            }

 也可以不判断开发环境