Pass a callback function reference to the System.Threading.Timer object

Question

you can pass a reference to the System.Threading.Timer object to your callback function, something like this:

System.Threading.Timer myTimer = new System.Threading.Timer(new TimerCallback(DoSomething), myTimer, 2000, Timeout.Infinite);

Because in the "DoSomething" method, I want to call:

myTimer.Change(5000, Timeout.Infinite);

I will attach the draft console application below. The idea is this: I have a list of timers. And each timer makes some kind of request, and when it receives it, it changes some general data. But I can’t pass the timer link into my callback and I can’t use it in the index, because for some reason (investigation) it becomes “-1”.

using System;
using System.Collections.Generic;
using System.Threading;

namespace TimersInThreads
{
    class Program
    {
        public static int sharedDataInt;
        static private readonly object lockObject = new object();
        public static List<System.Threading.Timer> timers = new List<Timer>();

        static void Main(string[] args)
        {
            System.Threading.Timer timer = new System.Threading.Timer(new TimerCallback(DoSomething), timers.Count - 1, 2000, Timeout.Infinite);
            timers.Add(timer);

            System.Threading.Timer timer2 = new System.Threading.Timer(new TimerCallback(DoSomething), timers.Count - 1, 2000, Timeout.Infinite);
            timers.Add(timer2);

            System.Threading.Timer timer3 = new System.Threading.Timer(new TimerCallback(DoSomething), timers.Count - 1, 2000, Timeout.Infinite);
            timers.Add(timer3);

            //timer = new System.Threading.Timer(new TimerCallback(DoSomething), "Timer 1", 1000, Timeout.Infinite);
            //timer = new System.Threading.Timer(new TimerCallback(DoSomething), "Timer 2", 450, Timeout.Infinite);
            //timer = new System.Threading.Timer(new TimerCallback(DoSomething), "Timer 3", 1500, Timeout.Infinite);

            Console.ReadLine();

        }

        static void DoSomething(object timerIndex)
        {
            // Request
            // Get Response
            var x = getSomeNumberWithDelay();


            // Executes after Response is received
            lock (lockObject)
            {
                sharedDataInt++;
                Console.WriteLine("Timer" + (int)timerIndex + ", SHaredDataInt: " + sharedDataInt + "\t\t" + DateTime.Now.ToString("HH:mm:ss tt") + "." + DateTime.Now.Millisecond.ToString());
            }

            timers[(int)timerIndex].Change(5000, Timeout.Infinite);
        }

        static int getSomeNumberWithDelay()
        {
            Thread.Sleep(5000);
            return 3;
        }
    }
}

Please give me some idea or advice. Thank you very much!

Answer 1

timers.Count - 1 timers.Count:

System.Threading.Timer timer = new System.Threading.Timer(new TimerCallback(DoSomething), timers.Count, 2000, Timeout.Infinite);
timers.Add(timer);

, , timers.Count 0.

- .

Answer 2

state TimerCallback - object, , .

So

new System.Threading.Timer(new TimerCallback(DoSomething), myTimer, 2000, Timeout.Infinite);

. Timer, .

static void DoSomething(object state)
{
    ...
    var timer = (System.Threading.Timer)state;
}

---

, , , (, , , ). , , , .

Timer t = null;
t = new Timer(delegate { DoSomething(t); }, null, 2000, Timeout.Infinite);

t .

Answer 3

. TypedCallback, . .

"", , , . , , .

/// <summary>
/// Holds a list of references to Timers; and provides typed objects to reference the Timer and its
/// State from within a TypedCallback. Synchronized. Usage:
/// <code>
/// TypedStateTimers myTimers = new TypedStateTimers(3);
/// public void MyMethod() {
///     typedStateTimers.Create("Hello, from Timer", new TypedCallback<string>((sr) => {
///         System.Console.WriteLine(sr.State); // "Hello, from Timer"
///         sr.Dispose(); // Invoke the StateRef method to ensure references are released
///     })).Start(1500, Timeout.Infinite);
/// }
/// </code>
/// </summary>
public class TypedStateTimers
{
    /// <summary>
    /// A typed delegate used as the callback when Timers are created.
    /// </summary>
    public delegate void TypedCallback<T>(StateRef<T> state);


    /// <summary>
    /// Wraps a Timer and State object to be used from within a TypedCallback.
    /// </summary>
    public class StateRef<T> : IDisposable
    {
        /// <summary>The state passed into TypedStateTimers.Create. May be null.</summary>
        public T State { get; internal set; }

        /// <summary>The Timer: initially not started. Not null.</summary>
        public System.Threading.Timer Timer { get; internal set; }

        /// <summary>The TypedStateTimers instance that created this object. Not null.</summary>
        public TypedStateTimers Parent { get; internal set; }


        /// <summary>
        /// A reference to this object is retained; and then Timer dueTime and period are changed
        /// to the arguments.
        /// </summary>
        public void Start(int dueTime, int period) {
            lock (Parent.Treelock) {
                Parent.Add(this);
                Timer.Change(dueTime, period);
            }
        }

        /// <summary>Disposes the Timer; and releases references to Timer, State, and this object.</summary>
        public void Dispose() {
            lock (Parent.Treelock) {
                if (Timer == null) return;
                Timer.Dispose();
                Timer = null;
                State = default(T);
                Parent.Remove(this);
            }
        }
    }


    internal readonly object Treelock = new object();
    private readonly List<IDisposable> stateRefs;


    /// <summary>
    /// Constructs an instance with an internal List of StateRef references set to the initialCapacity.
    /// </summary>
    public TypedStateTimers(int initialCapacity) {
        stateRefs = new List<IDisposable>(initialCapacity);
    }


    /// <summary>Invoked by the StateRef to add it to our List. Not Synchronized.</summary>
    internal void Add<T>(StateRef<T> stateRef) {
        stateRefs.Add(stateRef);
    }

    /// <summary>Invoked by the StateRef to remove it from our List. Not synchronized.</summary>
    internal void Remove<T>(StateRef<T> stateRef) {
        stateRefs.Remove(stateRef);
    }

    /// <summary>
    /// Creates a new StateRef object containing state and a new Timer that will use the callback and state.
    /// The Timer will initially not be started. The returned object will be passed into the callback as its
    /// argument. Start the Timer by invoking StateRef.Start. Dispose the Timer, and release references to it,
    /// state, and the StateRef by invoking StateRef.Dispose. No references are held on the Timer, state or
    /// the StateRef until StateRef.Start is invoked. See the class documentation for a usage example.
    /// </summary>
    public StateRef<T> Create<T>(T state, TypedCallback<T> callback) {
        StateRef<T> stateRef = new StateRef<T>();
        stateRef.Parent = this;
        stateRef.State = state;
        stateRef.Timer = new System.Threading.Timer(
                new TimerCallback((s) => { callback.Invoke((StateRef<T>) s); }),
                stateRef, Timeout.Infinite, Timeout.Infinite);
        return stateRef;
    }

    /// <summary>Disposes all current StateRef instances; and releases all references.</summary>
    public void DisposeAll() {
        lock (Treelock) {
            IDisposable[] refs = stateRefs.ToArray();
            foreach (IDisposable stateRef in refs) stateRef.Dispose();
        }
    }
}