When can I get an Application Insights operation id?

Think I finally cracked this without creating unwanted telemetry. The following is for AspNetCore, but should translate as long as the operation id initializer is available:

var operationId = default(string);
try
{
    var telemetry = new RequestTelemetry();

    TelemetryConfiguration
        .Active
        .TelemetryInitializers
        .OfType<OperationIdTelemetryInitializer>()
        .Single()
        .Initialize(telemetry);

    operationId = telemetry.Context.Operation.Id;

}
catch { }

I did not have OperationIdTelemetryInitializer in my TelemetryConfiguration .Active.TelemetryInitializers.

But this provides me with the current operation id:

System.Diagnostics.Activity.Current.RootId

https://github.com/Microsoft/ApplicationInsights-aspnetcore/issues/504