如何在asp.net web api应用中使用log4net.elmah.io包在elmah.io中设置URL、状态码、版本等参数？

Question

我使用log4net.elmah.io进行日志记录。

这是我的lo4net.config文件

<configuration>
 <configSections>
    <section name="log4net" type ="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
 </configSections>
 <log4net>
    <appender name="ElmahIoAppender" type="elmah.io.log4net.ElmahIoAppender, elmah.io.log4net">
      <logId value="LOG_ID" />
      <apiKey value="API_KEY" />
    </appender>
    <root>
      <level value="debug"/>
      <appender-ref ref="RollingFileAppender"/>
      <appender-ref ref="ElmahIoAppender" />
    </root>
  </log4net>
</configuration>

我已经为日志目的创建了一个名为MyFilterAttribute的类

using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;

namespace Resume
{
    public class MyFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            if (actionContext.Request.Method == HttpMethod.Get)
            {
                var log = log4net.LogManager.GetLogger(typeof(ApiController));
                log.Info("This is log meassage for GET method");
            }

        }
    }
}

在控制器的操作方法之前提到MyFilterAttribute，如下所示：

[Route("api/employees/{id}")]
[HttpGet]
[MyFilterAttribute]
public HttpResponseMessage GetEmployee(int id)
 {
    var employee = _unitOfWork.Employee.Get(id);

    return employee != null? Request.CreateResponse(HttpStatusCode.OK, employee) : Request.CreateErrorResponse(HttpStatusCode.NotFound, "Employee with Id " + id + " does not exist");
}

当请求发出时，我能够得到响应和日志消息。

elmah.io中的输出图像如下：https://ibb.co/QrFBQdx

有关elmah.io的输出，请参阅图像的URL

在这里，您可以看到URL和状态代码未被记录。

谁来帮我解决这个问题。

Answer 1

您可以将以下代码放入Global.asax.cs的Application_Start方法中

public class WebApiApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        ...

        Hierarchy hier = log4net.LogManager.GetRepository() as Hierarchy;
        var elmahIoAppender = (ElmahIoAppender)(hier?.GetAppenders())
            .FirstOrDefault(appender => appender.Name
                .Equals("ElmahIoAppender", StringComparison.InvariantCultureIgnoreCase));

        elmahIoAppender.ActivateOptions();
        elmahIoAppender.Client.Messages.OnMessage += (sender, a) =>
        {
            var ctx = HttpContext.Current;
            if (ctx == null) return;
            a.Message.Url = ctx.Request?.Path;
            a.Message.StatusCode = ctx.Response?.StatusCode;
        };
    }
}

这会导致每条日志消息都会触发OnMessage回调。如果在记录时存在HTTP上下文，则会在记录到elmah.io的消息上填充Url和StatusCode字段。