在 ASP.NET Core MVC 中捕获异常

Question

我已经在 ASP.NET MVC Core 中看到了多种捕获异常的方法，但我需要了解为什么我所做的没有按预期工作。

我添加了以下内容：

public abstract class GenericActionFilter : ActionFilterAttribute

{

    protected readonly ILog Logger = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

    public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)

    {

        if (await OnBeforeActionExecutionAsync(context))

        {

            var executed = await next();

            if (executed.Exception != null && !executed.ExceptionHandled)

            {

                await OnExceptionAsync(context, executed.Exception);

            }

            else

            {

                await OnAfterActionExecutionAsync(context);

            }

        }

    }

    public virtual Task<bool> OnBeforeActionExecutionAsync(ActionExecutingContext context)

    {

        return Task.FromResult(true);

    }

    public virtual Task OnAfterActionExecutionAsync(ActionExecutingContext context)

    {

        return Task.CompletedTask;

    }

    public virtual Task OnExceptionAsync(ActionExecutingContext context, Exception ex)

    {

        return Task.CompletedTask;

    }

}

并像这样使用它：

public class ExceptionFilter : GenericActionFilter

{

    public IntegrationScenarioSettings Settings { get; set; }

    public override Task OnExceptionAsync(ActionExecutingContext context, Exception ex)

    {

        context.Result = new ContentResult

        {

            Content = Settings.ApiExecutionExceptionMessage,

            StatusCode = (int)HttpStatusCode.ServiceUnavailable

        };

        //outputs to endpoint.log

        Logger.Error(ex);

        return Task.CompletedTask;

    }

}

动作中的底层代码抛出异常，而不是看到 503，我仍然是 500。

我在这里缺少什么？

Answer 1

为了通知 ASP.NET Core MVC 管道您已处理异常，您需要设置ActionExecutedContext.ExceptionHandled为true. 因为您在显示的代码中没有此功能，所以 ASP.NET Core MVC 管道使用其自己的错误处理逻辑将您的（它认为是）未处理的异常转换为 500 响应。现在 - 此属性存在于ActionExecutedContext而不是ActionExecutingContext（您在代码中使用）。这是有道理的，因为它ActionExecutingContext代表了动作运行之前的状态，也代表了动作运行之后的ActionExecutedContext状态。这意味着您将需要以下一组更改：更新你的OnExceptionAsync函数来ActionExecutedContext代替ActionExecutingContext.更新对 的调用OnExceptionAsync，提供executed而不是context。当您在这里时，您还可以将方法参数折叠为仅 executed（我将在下面的代码中显示）。设置context.ExceptionHandled为true一旦你已经处理了异常。:)我已经从您的问题中获取了代码，删除了一些与问题无关的代码并应用了这些更改，我用上面的相应数字调用了这些更改：public abstract class GenericActionFilter : ActionFilterAttribute{&nbsp; &nbsp; public override async Task OnActionExecutionAsync(ActionExecutingContext context,&nbsp; &nbsp; &nbsp; &nbsp; ActionExecutionDelegate next)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; if (await OnBeforeActionExecutionAsync(context))&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var executed = await next();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (executed.Exception != null && !executed.ExceptionHandled)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; await OnExceptionAsync(executed); // #2.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; else&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // NOTE: You might want to use executed here too.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; await OnAfterActionExecutionAsync(context);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; // ...&nbsp; &nbsp; public virtual Task OnExceptionAsync(ActionExecutedContext context) // #1.&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; return Task.CompletedTask;&nbsp; &nbsp; }}public class ExceptionFilter : GenericActionFilter{&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; public override Task OnExceptionAsync(ActionExecutedContext context) // #1, #2.&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; Logger.Error(context.Exception); // #2 (single parameter).&nbsp; &nbsp; &nbsp; &nbsp; context.Result = new ContentResult { ... };&nbsp; &nbsp; &nbsp; &nbsp; context.ExceptionHandled = true; // #3.&nbsp; &nbsp; &nbsp; &nbsp; return Task.CompletedTask;&nbsp; &nbsp; }}