ASP.NET Core Web API通过中间件或UseExceptionHandler异常处理方法

1、使用中间件(middleware)异常处理

1）中间件代码

public class ErrorHandlingMiddleware{    private readonly RequestDelegate next;    public ErrorHandlingMiddleware(RequestDelegate next)    {        this.next = next;    }    public async Task Invoke(HttpContext context /* other dependencies */)    {        try        {            await next(context);        }        catch (Exception ex)        {            await HandleExceptionAsync(context, ex);        }    }    private static Task HandleExceptionAsync(HttpContext context, Exception ex)    {        var code = HttpStatusCode.InternalServerError; // 500 if unexpected        if      (ex is MyNotFoundException)     code = HttpStatusCode.NotFound;        else if (ex is MyUnauthorizedException) code = HttpStatusCode.Unauthorized;        else if (ex is MyException)             code = HttpStatusCode.BadRequest;        var result = JsonConvert.SerializeObject(new { error = ex.Message });//JsonConvert.SerializeObject(errorObj, opts.Value.SerializerSettings)        context.Response.ContentType = "application/json";        context.Response.StatusCode = (int)code;        return context.Response.WriteAsync(result);    }}

2）在Startup.cs注册中间件

注意：要在app.UseMvc();之前注册。

app.UseMiddleware(typeof(ErrorHandlingMiddleware));
app.UseMvc();

2）输出异常信息的JSON格式

{ "error": "Authentication token is not valid." }

2、使用app.UseExceptionHandler()异常处理

app.UseExceptionHandler(a => a.Run(async context =>{    var feature = context.Features.Get();    var exception = feature.Error;    var result = JsonConvert.SerializeObject(new { error = exception.Message });    context.Response.ContentType = "application/json";    await context.Response.WriteAsync(result);}));

3、使用Community.AspNetCore.ExceptionHandling异常处理

1）需要引用的Nuget包

ASP.NET Core 2.0：Community.AspNetCore.ExceptionHandling.NewtonsoftJson 

ASP.NET Core 2.1+：Community.AspNetCore.ExceptionHandling.Mvc

相关文档：VS(Visual Studio)中Nuget的使用

2）配置使用示例代码

public void ConfigureServices(IServiceCollection services){    services.AddMvc();    services.AddExceptionHandlingPolicies(options =>    {        options.For().Rethrow();        options.For().Retry(ro => ro.MaxRetryCount = 2).NextPolicy();        options.For()        .Response(e => 400)            .Headers((h, e) => h["X-MyCustomHeader"] = e.Message)            .WithBody((req,sw, exception) =>                {                    byte[] array = Encoding.UTF8.GetBytes(exception.ToString());                    return sw.WriteAsync(array, 0, array.Length);                })        .NextPolicy();        // 确保所有异常类型都通过在末尾添加通用异常的处理程序来处理。        options.For()        .Log(lo =>            {                lo.EventIdFactory = (c, e) => new EventId(123, "UnhandlerException");                lo.Category = (context, exception) => "MyCategory";            })        .Response(null, ResponseAlreadyStartedBehaviour.GoToNextHandler)            .ClearCacheHeaders()            .WithObjectResult((r, e) => new { msg = e.Message, path = r.Path })        .Handled();    });}public void Configure(IApplicationBuilder app, IHostingEnvironment env){    app.UseExceptionHandlingPolicies();    app.UseMvc();}