谁能解释IExceptionHandler与样品客户端应用程序的工作流程

问题描述

我面临的问题，下面这个示例：

我无法找到 IsOutermostCatchBlock 在 ExceptionContext

如果出现异常，这 HandleAsync 方法被执行了两次。

（http://www.asp.net/web-api/overview/web-api-routing-and-actions/web-api-global-error-handling)

 公共类CustomExceptionHandler：IExceptionHandler
{
    公共虚拟任务HandleAsync（ExceptionHandlerContext的背景下，
                                        的CancellationToken的CancellationToken）
    {
        如果（！ShouldHandle（上下文））
        {
            返回Task.FromResult（0）;
        }            返回HandleAsyncCore（背景下，的CancellationToken）;
        }        公共虚拟任务HandleAsyncCore（ExceptionHandlerContext的背景下，
                                            的CancellationToken的CancellationToken）
        {
            HandleCore（上下文）;
            返回Task.FromResult（0）;
        }        公共虚拟无效HandleCore（ExceptionHandlerContext上下文）
        {
        }        公共虚拟BOOL ShouldHandle（ExceptionHandlerContext上下文）
        {
             返回context.ExceptionContext.IsOutermostCatchBlock;
        }    }    公共类OopsExceptionHandler：CustomExceptionHandler
    {
        公共覆盖无效HandleCore（ExceptionHandlerContext上下文）
        {
            context.Result =新TextPlainErrorResult
            {
                请求= context.ExceptionContext.Request，
                CONTENT =哎呀！对不起！出事了。 +
                          请联系[email protected]所以我们可以尝试修复它。
            };
        }        私有类TextPlainErrorResult：IHttpActionResult
        {
            公众的Htt prequestMessage请求{搞定;组; }
            公共字符串内容{搞定;组; }            公共任务＆LT; Htt的presponseMessage＆GT; ExecuteAsync（的CancellationToken的CancellationToken）
            {
                HTT presponseMessage响应=
                                 新的Htt presponseMessage（的HTTPStatus code.InternalServerError）;
                response.Content =新的StringContent（内容）;
                response.RequestMessage =请求;
                返回Task.FromResult（响应）;
            }
        }
    }
}
 

解决方案

CatchBlock.IsTopLevel

IsOutermostCatchBlock 不存在。
使用 CatchBlock.IsTopLevel 而不是：

 公共虚拟BOOL ShouldHandle（ExceptionHandlerContext上下文）
{
  返回context.ExceptionContext.CatchBlock.IsTopLevel;
}
 

在NuDoq来源：ExceptionHandlerContext和ExceptionContextCatchBlock

I am facing below issues in this Sample:

I am not able to find IsOutermostCatchBlock in ExceptionContext

If Exception occurs, this HandleAsync method is executing twice.

(http://www.asp.net/web-api/overview/web-api-routing-and-actions/web-api-global-error-handling)

public class CustomExceptionHandler : IExceptionHandler
{
    public virtual Task HandleAsync(ExceptionHandlerContext context,
                                        CancellationToken cancellationToken)
    {
        if (!ShouldHandle(context))
        {
            return Task.FromResult(0);
        }

            return HandleAsyncCore(context, cancellationToken);
        }

        public virtual Task HandleAsyncCore(ExceptionHandlerContext context,
                                            CancellationToken cancellationToken)
        {
            HandleCore(context);
            return Task.FromResult(0);
        }

        public virtual void HandleCore(ExceptionHandlerContext context)
        {
        }

        public virtual bool ShouldHandle(ExceptionHandlerContext context)
        {
             return context.ExceptionContext.IsOutermostCatchBlock;
        }

    }

    public class OopsExceptionHandler : CustomExceptionHandler
    {
        public override void HandleCore(ExceptionHandlerContext context)
        {
            context.Result = new TextPlainErrorResult
            {
                Request = context.ExceptionContext.Request,
                Content = "Oops! Sorry! Something went wrong." +
                          "Please contact [email protected] so we can try to fix it."
            };
        }

        private class TextPlainErrorResult : IHttpActionResult
        {
            public HttpRequestMessage Request { get; set; }
            public string Content { get; set; }

            public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
            {
                HttpResponseMessage response =
                                 new HttpResponseMessage(HttpStatusCode.InternalServerError);
                response.Content = new StringContent(Content);
                response.RequestMessage = Request;
                return Task.FromResult(response);
            }
        }
    }
}

解决方案

CatchBlock.IsTopLevel

IsOutermostCatchBlock does not exists.Use CatchBlock.IsTopLevel instead:

public virtual bool ShouldHandle(ExceptionHandlerContext context)
{
  return context.ExceptionContext.CatchBlock.IsTopLevel;
}

Source on NuDoq: ExceptionHandlerContext and ExceptionContextCatchBlock

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