如何在方法之间传递跟踪 id 而无需在 C# 中作为参数传递？

Question

Let's say I have two methods

public async Task A()
{
   var traceId = Guid.NewGuid().ToString();
   Log($"{traceId}-Method A was called");
   await B(traceId);
}

public async Task B(string traceId)
{
   Log($"{traceId}-Method B was called");
}

I need to keep a log of the execution path. For this I need to pass a trace id but this clutters the code. Is there a better way to persist these types of information in C# method calls?

PS: Method A and B could be in different c# assemblies as well. This is a web application.

Answer 1

Ideally, you would use a tracing/logging system that already provides this functionality, eg, Activity has an Id .

But if you want to build your own, you can use AsyncLocal<T> :

private static readonly AsyncLocal<string> traceId = new();

private static IDisposable SetTraceId(string id)
{
  var oldValue = traceId.Value;
  traceId.Value = id;
  return new Disposable(() => traceId.Value = oldValue);
}

public async Task A()
{
  using var _ = SetTraceId(Guid.NewGuid().ToString());
  Log($"{traceId.Value}-Method A was called");
  await B();
}

public async Task B()
{
  Log($"{traceId.Value}-Method B was called");
}

( Disposable is from my Disposables library )

My recommendations for working with AsyncLocal<T> are:

1. Always use immutable types for T . Otherwise the code can get very confusing.
2. When setting AsyncLocal<T>.Value , use a disposable like the code above does to reset it. Again, this makes the code less confusing.