<PackageReference Include="NETStandard.Library" Version="2.0.0-preview2-25401-01" />

System.Timers.Timer

namespace System.Timers { public class Timer : Component, ISupportInitialize { public bool AutoReset { get; set; } public bool Enabled { get; set; } public double Interval { get; set; } public ISynchronizeInvoke SynchronizingObject { get; set; } public event ElapsedEventHandler Elapsed; public Timer(); public Timer(double interval); public void BeginInit(); public void Close(); public void EndInit(); public void Start(); public void Stop(); } }