TraceEvent.EventName missing when OpCode assigned to event

[aaronhudon]

Using Microsoft.Diagnostics.Tracing.TraceEvent 2.0.55 with .NET Core 3.1.201

When an eventsource event is assigned an OpCode (e.g. Start, Stop), then the event reaches the TraceEventSession, the TraceEvent object's EventName is missing, and simply contains "/Start" or "/Stop" based on the OpCode.

This seems to be resolved by simply removing the Start/Stop OpCodes and applying the magic "Start" and "Stop" suffix to the event source method names...I'd prefer to use the OpCodes as it's explicit and not relying on magic.

[brianrob]

@aaronhudon how are you collecting the trace where this occurs? Is this, ETW or dotnet-trace?

[aaronhudon]

@brianrob Hi Brian, I'm collecting through a .net core 3.1 application using Using Microsoft.Diagnostics.Tracing.TraceEvent
I guess you could call this ETW

[brianrob]

@aaronhudon, thanks for reporting this. I was able to reproduce the behavior you're seeing with this test case:

using System;
using System.Diagnostics.Tracing;

namespace eventsource_helloworld
{
    class Program
    {
        static void Main(string[] args)
        {
            TestEventSource.Log.Begin();
            Console.WriteLine("Hello World!");
            TestEventSource.Log.End();
        }
    }

    [EventSource(Name = "TestEventSource")]
    public sealed class TestEventSource : EventSource
    {
        public static TestEventSource Log = new TestEventSource();

        private TestEventSource()
        {
        }

        [Event(1, Opcode = EventOpcode.Start)]
        public void Begin()
        {
            WriteEvent(1);
        }

        [Event(2, Opcode = EventOpcode.Stop)]
        public void End()
        {
            WriteEvent(2);
        }
    }
}

From some testing, this appears to be an issue specific to EventSource. Opening the trace in PerfView and WPA yields the same result.

WPA:

PerfView:

@sywhang, @josalem can you please take a look?

[sywhang]

@brianrob I'll take a look at it today. Thanks