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Posted 25 Jan 2013

Event traffic calming

, 26 Jan 2013 CPOL
How to build an object to calm down event traffic.
using System;
using System.Linq.Expressions;
using System.Threading;
using NUnit.Framework;

namespace TrafficCalming.Tests
    public class EventCalmerFixture
        private static readonly TimeSpan WaitTime = TimeSpan.FromMilliseconds(100);

        private EventCalmer _calmer;

        public void Setup()
            _calmer = new EventCalmer(WaitTime);

        public void Can_create_instances()
            Assert.That(_calmer, Is.Not.Null);

        public void HandleEvent_triggers_EventOcurred_as_soon_as_posible()
            var untilEventHasBeenTriggered = new ManualResetEvent(false);
            _calmer.EventOccurred += (s,e) => 

            _calmer.HandleEvent(this, EventArgs.Empty);

            var didNotTimedOut = untilEventHasBeenTriggered.WaitOne(1000);

        public void HandleEvent_twice_triggers_EventOcurred_only_once_in_time_frame_smaller_than_waitime()
            var eventOcurredTriggeredCount = 0;
            _calmer.EventOccurred += (s, e) =>

            _calmer.HandleEvent(this, EventArgs.Empty);
            _calmer.HandleEvent(this, EventArgs.Empty);

            Assert.That(eventOcurredTriggeredCount, Is.LessThan(2));

        public void HandleEvent_does_not_block_main_thread()
            _calmer.EventOccurred += (s, e) =>

            ExecuteWithTimeout(() => 
                _calmer.HandleEvent(this, EventArgs.Empty), 10);

        private static void ExecuteWithTimeout(Expression<Action> expression, int timeoutMillis)
            var untilActionFinishes = new ManualResetEvent(false);
            var action = expression.Compile();
            Action actionAsync = 
                () =>

            actionAsync.BeginInvoke(null, null);
            if (!untilActionFinishes.WaitOne(timeoutMillis))
                throw new Exception("Execution timed out for expression: '" + expression + "'");

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About the Author

Erich Ledesma
Architect SunHotels
Spain Spain
I Received a Bachelor's Degree in Computer Science at the Mathematics and Computer Science Faculty, University of Havana, Cuba.

I mainly work in web applications using C# and some Javascript. Some very few times do some Java.

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