NLog，访问自定义目标中的布局渲染器

Question

我正在创建一个自定义目标，但我看不到访问布局渲染器值(如aspnet traceidentifier(的方法https://github.com/NLog/NLog/wiki/AspNetTraceIdentifier-Layout-Rendererfrom Write方法。

这是我使用的代码：

[Target("CustomTarget")]
public sealed class CustomTarget : AsyncTaskTarget
{
protected override async Task WriteAsyncTask(LogEventInfo logEvent, CancellationToken token)
{
var layout = new NLog.Layouts.SimpleLayout("${aspnet-traceidentifier}");
string logMessage = this.Layout.Render(logEvent);
string identifier = layout.Render(logEvent);
// identifier is empty here...

identifier = RenderLogEvent("${aspnet-traceidentifier}", logEvent);

// identifier is empty here...
}  
}

Answer 1

也许是这样的：

[Target("CustomTarget")] 
public sealed class CustomTarget : AsyncTaskTarget
{ 
public CustomTarget()
{
this.CorrelationId = "${aspnet-traceidentifier}";
}

public Layout CorrelationId { get; set; }

protected override Task WriteAsyncTask(LogEventInfo logEvent, CancellationToken token)
{ 
string logMessage = this.RenderLogEvent(this.Layout, logEvent); 
string correlationId = this.RenderLogEvent(this.CorrelationId, logEvent); 
// TODO - write message
} 
} 

另请参阅编写自定义NLog目标的教程：https://github.com/NLog/NLog/wiki/How-to-write-a-custom-async-target