一、過濾器方式

先定義一個異常過濾器

    /// <summary>
    /// 異常過濾器
    /// </summary>
    public class ExceptionFilter : IExceptionFilter
    {
        /// <summary>
        /// 發生異常時進入
        /// </summary>
        /// <param name="context"></param>
        public void OnException(ExceptionContext context)
        {
            
 
if (context.ExceptionHandled == false)
            {
                context.Result = new ContentResult
                {
                    Content = context.Exception.Message,//這裡是把異常輸出，也可以不輸出，也可以輸出JSON結構的字串。
          StatusCode = StatusCodes.Status200OK,
                    ContentType = "text/html;charset=utf-8
 
"
                };
            }
            context.ExceptionHandled = true;

            //寫入日誌，或者其它操作
            
        }
    }

再API控制器使用過濾器

[TypeFilter(typeof(ExceptionFilter))]//這裡使用自定義過濾器
[ApiController]
public class MyController:ControllerBase
{
    //.....          
}

二、配置方式

在Startup.cs中的，Configure

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //異常配置檔案寫法
            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;

                            //輸出異常內容，也可以不輸出，也可以輸出JSON結構的字串
                            await context.Response.WriteAsync(ex.Message);
                        }
                    });
                });
            }
        }

三、中介軟體方式

先定義一個異常中介軟體

    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)
            {
                //寫入日誌或者其它操作
                //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";
            //輸出異常內容
            await httpContext.Response.WriteAsync(ex.Message);
            //如果不輸出，則需要下面這句
            //return Task.CompletedTask;
        }
    }

再定義一個擴充套件類

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

在Startup的Configure中配置

            //異常配置檔案寫法
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseCustomExceptionMiddleware();
            }

也可以不判斷開發環境