using System.Collections.Generic; using System.Runtime.CompilerServices; namespace System.Diagnostics.Metrics { public abstract class ObservableInstrument<T> : Instrument where T : struct { public override bool IsObservable => true; [System.Runtime.CompilerServices.NullableContext(1)] protected ObservableInstrument(Meter meter, string name, [System.Runtime.CompilerServices.Nullable(2)] string unit, [System.Runtime.CompilerServices.Nullable(2)] string description) : base(meter, name, unit, description) { Instrument.ValidateTypeParameter<T>(); } [return: System.Runtime.CompilerServices.Nullable(new byte[] { 1, 0, 0 })] protected abstract IEnumerable<Measurement<T>> Observe(); internal override void Observe(MeterListener listener) { object subscriptionState = GetSubscriptionState(listener); IEnumerable<Measurement<T>> enumerable = Observe(); if (enumerable != null) { foreach (Measurement<T> item in enumerable) { listener.NotifyMeasurement<T>((Instrument)this, item.Value, item.Tags, subscriptionState); } } } [MethodImpl(MethodImplOptions.AggressiveInlining)] internal static IEnumerable<Measurement<T>> Observe(object callback) { Func<T> func = callback as Func<T>; if (func != null) return new Measurement<T>[1] { new Measurement<T>(func()) }; Func<Measurement<T>> func2 = callback as Func<Measurement<T>>; if (func2 != null) return new Measurement<T>[1] { func2() }; return (callback as Func<IEnumerable<Measurement<T>>>)?.Invoke(); } } }