Not sure if this is the right repository, or if still relevant as I could not find the source code of EventSource here.

Some minor improvement I noticed while benchmarking allocations on our code, I think could be traced to the call to Add on the list in this line

    List<object> arg = new List<object>();
    arg.Add(msg);

could be changed to:

    List<object> arg = new List<object>(new []{ msg });