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How to queue incoming events in event handler while waiting for user's response

I use C#, .NET Framework 4.5, VS2015.
I implement an event handler for event (TcpRequest) that is fired by a black-boxed module.
My event handler call a private method that fires an event to client/GUI and waiting for user's response.
Meanwhile the black-boxed module keeps firing TcpRequest event. Somehow I need to queue the incoming events while waiting.
As soon as the user gives response for the first event, the queue can be "flushed".
Is there any design pattern or best practice for such case (to queue while wait for user's response)? Do I need to use await or something?
Following are my codes. Please feel free to modify them. Thank you in advance.
public void TcpRequestHandler(int id, CONN_INFO connInfo)
{
if (SomeCondition)
{
var myArgs = new MyEventArgs()
{
Id = id,
ConnInfo = connInfo
}
// this the way I tried and I know it is wrong,
// because it always fires event without "waiting in queue"
lock (_eventQueue)
{
_eventQueue.Add(myArgs);
}
FireEventToClient(myArgs);
}
}
private void FireEventToClient(MyEventArgs myArgs)
{
EventToClient(this, myArgs);
if (myArgs.Continue)
{
// "flush" the event queue
...
// do other things
...
}
}
public class MyEventArgs : EventArgs
{
public int Id {get; private set;}
public CONN_INFO ConnInfo {get; private set;}
public bool Continue {get; set;}
}

Declare your event EventToClient with return value and use the returned value for validation and flush the event queue

Check this, it may help
public class TCPServer
{
private int _port;
private TcpListener _tcpListener;
private bool _running, _disposed;
private BinaryFormatter _bFormatter;
private Thread _connectionThread;
private BackgroundWorker _bgwListener;
private BackgroundWorker _bgwSender;
private object syncobject = new object();
private object syncsendmessageobject = new object();
/// <summary>
/// Constructor - Initialises the TCPServer with the given port and a tcplistener. Starts a thread to monitor the message queue
/// </summary>
/// <param name="port"></param>
public TCPServer(int port)
{
try
{
this._port = port;
this._tcpListener = new TcpListener(IPAddress.Loopback, port);
this._running = false;
this._bFormatter = new BinaryFormatter();
Thread thread = new Thread(ReadQueue);
thread.Start();
}
catch (Exception ex)
{
}
}
/// <summary>
/// Starts the tcplistener.
/// </summary>
public void Start()
{
try
{
if (!_running)
{
this.MessageReceived -= TCPServer_MessageReceived;
this._tcpListener.Start();
this._running = true;
this._connectionThread = new Thread(new ThreadStart(ListenForClientConnections));
this._connectionThread.Start();
this._connectionThread.IsBackground = true;
this.MessageReceived += TCPServer_MessageReceived;
}
}
catch (Exception ex)
{
}
}
/// <summary>
/// Stops the tcplistener
/// </summary>
public void Stop()
{
if (this._running)
{
this._tcpListener.Stop();
this._tcpListener = null;
this._running = false;
}
}
public bool Running()
{
return this._running;
}
public void StopListening()
{
try
{
lock (this)
{
if (this._running)
{
this._tcpListener.AcceptTcpClient().Close();
_running = false;
}
}
}
catch (Exception ex)
{
}
}
/// <summary>
/// Thread body for listening for client connections
/// </summary>
private void ListenForClientConnections()
{
try
{
while (this._running)
{
lock (this)
{
TcpClient connectedTcpClient = this._tcpListener.AcceptTcpClient();
this._bgwListener = new BackgroundWorker();
this._bgwListener.DoWork += _bgwListener_DoWork;
this._bgwListener.WorkerReportsProgress = true;
this._bgwListener.ProgressChanged += _bgwListener_ProgressChanged;
this._bgwListener.RunWorkerAsync(connectedTcpClient);
}
}
}
catch (Exception ex)
{
}
}
/// <summary>
/// background worker listens to messages sent by clients. Categorises them based on messages/commands/applicationcommands/
/// progress response etc..
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private TcpClient clientGUI = null;
private Queue<string> messageQueue = new Queue<string>();
private void _bgwListener_DoWork(object sender, DoWorkEventArgs e)
{
TcpClient client = e.Argument as TcpClient;
BackgroundWorker bgWorker = sender as BackgroundWorker;
if (client != null)
{
try
{
while (this._running)
{
// Block until an instance Message is received
string message = this._bFormatter.Deserialize(client.GetStream()).ToString();
if (message.Equals("GUI", StringComparison.InvariantCultureIgnoreCase)
{
// Chek for first message from tcp client, if it is GUI then store it in a member variable, if you have multiple cleints then use a dictionary
clientGUI = client;
}
if(!clientGUI.Equals(client))
{
lock (syncobject)
{
messageQueue.Enqueue(message);
}
}
}
}
catch (Exception ex)
{
}
}
}
/// <summary>
/// Thread that continuously monitors the message queue for messages and
/// sends them to clients
/// </summary>
private void ReadQueue()
{
try
{
while (true)
{
try
{
TCPMessage message = null;
if (messageQueue.Count > 0)
{
lock (syncobject)
{
message = messageQueue.Dequeue();
}
if (!string.IsNullOrEmpty(message) && clientGUI != null)
{
SendMessage(clientGUI, message);
}
}
else { Thread.Sleep(10); }
}
catch (Exception ex)
{
}
}
}
catch (Exception ex)
{
}
}
private MessageReceivedEventHandler _messageReceived;
public event MessageReceivedEventHandler MessageReceived
{
add { _messageReceived += value; }
remove { _messageReceived -= value; }
}
private EventHandler<MessageEventArgs> _serverMessageSent;
public event EventHandler<MessageEventArgs> ServerMessageSent
{
add { _serverMessageSent += value; }
remove { _serverMessageSent -= value; }
}
private void SendMessage(TcpClient client, TCPMessage message)
{
try
{
lock (syncsendmessageobject)
_bFormatter.Serialize(client.GetStream(), message);
}
catch (Exception ex)
{
}
}
}

Delegate SystemAction as constructor parameter

I have a winform I'm working on that needs change a label when it hits a specific phase and the same label when it's complete. I have an interface setup and a class that implements this interface. In the class constructor, I'm trying to add the Action<> as a parameter but I am having trouble processing what I need to do in order to get it to flow correctly.
Never could get it to work :/

While your example i cannot give specific example because it confuses me. I can still answer some questions.
Does this help?
private Action _methodOnProgress;
public ChipLoadFirmware(Action method)
{
_methodOnProgress = method;
}
public bool LoadFirmWare()
{
(p) = >
{
_methodOnProgress();
}
}

Maybe an event pattern here will be more reliable.
First add a
public event EventHandler Progress
to your ChipLoadFirmware class, and make it public in the manager class (lets assume it's called Manager and the ChiLoad instance is called Loader)
So, when you instance the manager in the form you add
Manager.Loader.Progress += (o, e) => { /* Change the label */ };
And finally in the (p) => { } do
Progress(this, EventArgs.Empty);
EDIT Here is your code with the changes, supose the class Form is your form and labelToChange the label which must be changed;
/// <summary>
/// Represents an object that can load the firmware
/// </summary>
public interface ILoadFirmware
{
/// <summary>
/// Loads firmware on a device
/// </summary>
bool LoadFirmware();
event EventHandler Progress;
event EventHandler Status;
}
public class ChipLoadFirmware : ILoadFirmware
{
private readonly log4net.ILog logger = Logging.Log4NetManager.GetLogger();
private readonly ImageLoader imageLoader = new ImageLoader ();
private bool abort = false;
private string cmdText = string.Empty;
private string errortext = string.Empty;
private string isaIp;
public event EventHandler Progress;
public event EventHandler Status;
/// <summary>
/// Sets up an ImageLoader
/// </summary>
/// <param name="isaTargetIpAddress">The IP address of the ISA to load the firmware on</param>
public ChipLoadFirmware (string isaTargetIpAddress)
{
this.isaIp = isaTargetIpAddress;
imageLoader.EventHandler += (s, e) => { };
logger.DebugFormat("Using IP Address {0}", isaTargetIpAddress);
}
/// <summary>
/// Loads the firmware onto the device
/// </summary>
/// <returns>Returns true if successful</returns>
public bool LoadFirmware()
{
bool result = imageLoader.Run(this.isaIp,
false,
Command.Command,
string.Empty,
CommandFlag.CommandFlag,
2000,
(p) => { Progress(this, EventArgs.Empty); },
(s) => { Status(this, EventArgs.Empty); },
ref this.abort,
out this.cmdText,
out this.errortext);
if (!result)
{
result = false;
throw new InvalidOperationException(
string.Format(
"ImageLoader failed with message: {0}",
errortext));
}
return result;
}
}
public class CalibrationManager : ICalibrationManager
{
const uint startAddress = 0x00000000;
const uint startAddress = 0x00000000;
private readonly log4net.ILog logger;
private readonly ISignalGenerator sigGenerator;
public readonly ILoadFirmware loadFirmware;
private readonly IReader reader;
private readonly IValueParser valueParser;
private readonly IRepository<CalibrationValue> calibrationRepository;
private readonly IRepository<UIDList> uidRepository;
private string uid;
public CalibrationManager(ISignalGenerator sigGen, ILoadFirmware loadFirmware, IReader chipRreader, IValueParser chipValueParser, IRepository<UIDList> uidRepo, IRepository<CalibrationValue> calRepo)
{
if (sigGen == null ||
loadFirmware == null ||
chipReader == null ||
chipValueParser == null ||
calRepo == null ||
uidRepo == null) throw new ArgumentNullException();
logger = Logging.Log4NetManager.GetLogger();
this.sigGenerator = sigGen;
this.loadFirmware = loadFirmware;
this.reader = chipReader;
this.valueParser = chipValueParser;
this.uidRepository = uidRepo;
this.calibrationRepository = calRepo;
}
public void Calibrate(bool reuse)
{
int voltageG;
int currentG;
// Read uid from device
this.uid = uidReader.ReadUid();
logger.DebugFormat("Read UID {0}", this.uid);
var possibleCalibrations = getCalibrationDataFromRepo();
if (possibleCalibrations.Any() && reuse)
{
logger.Debug("Reusing existing values");
var existingCalibration = possibleCalibrations.OrderByDescending(c => c.DateCalibrated).First();
currentG = existingCalibration.CurrentGain;
voltageG = existingCalibration.VoltageGain;
}
else
{
logger.Debug("Reading new values");
// Set voltage and current for signal generator
sigGenerator.SetOutput(187, 60);
// Load firmware onto chip for CLI commands
loadFirmware.LoadFirmware();
UpdateStateChange(StateOfDevice.LoadFirmware);
// Read voltage from device and calibrate
voltageG = valueParser.ReadVoltageValue();
UpdateStateChange(StateOfDevice.CalibrateVoltage);
// Read current from device and calibrate
sigGenerator.SetOutput(38, 60);
currentG = valueParser.ReadCurrentValue();
UpdateStateChange(StateOfDevice.CalibrateCurrent);
// Insert values into table
CalibrationValue cv = new CalibrationValue();
cv.UidId = uidRepository.GetBy(e => e.UID.Equals(this.uid)).Id;
cv.CurrentGain = currentG;
cv.VoltageGain = voltageG;
calibrationRepository.Insert(cv);
calibrationRepository.Submit();
UpdateStateChange(StateOfDevice.DatabaseInsert);
}
logger.DebugFormat("Updated database for current gain to {0} and voltage gain to {1}", currentG, voltageG);
// Once here, device has passed all phases and device is calibrated
UpdateStateChange(StateOfDevice.CalibrationComplete);
}
private IQueryable<CalibrationValue> getCalibrationDataFromRepo()
{
int uidId = uidRepository.GetBy(e => e.UID.Equals(this.uid)).Id;
return calibrationRepository.SearchFor(c => c.UidId == uidId);
}
public bool CalibrationDataExists()
{
this.uid = uidReader.ReadUid();
logger.DebugFormat("Read UID {0}", this.uid);
return getCalibrationDataFromRepo().Any();
}
public event Action<StateOfDevice, string> StateChange;
private void UpdateStateChange(StateOfDevice state, string message = "")
{
var sc = StateChange;
if (sc != null)
{
StateChange(state, message);
}
}
}
public class Form
{
Label labelToModify;
void MagickButtonClick(object Source, EventArgs e)
{
CalibrationManager manager = new CalibrationManager(.......);
manager.loadFirmware.Progress += (o, e) => { labelToModify.Text = "Some progress achieved!!"; };
}
}

Timer in portable class library

I've made a timer class based on this discussion but I have a problem with it, the elapsed event occurs only one time.
The smaller issue: It would be a good thing if the _timer not have to be instantiated at every calling of Start().
using System;
using System.Threading;
using System.Threading.Tasks;
using System.Diagnostics.Contracts;
namespace JellystonePark.Model
{
internal delegate void TimerCallback(object state);
internal sealed class Timer : CancellationTokenSource, IDisposable
{
internal Timer(TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period)
{
Contract.Assert(period == TimeSpan.FromMilliseconds(-1), "This stub implementation only supports dueTime.");
Task.Delay(dueTime, Token).ContinueWith((t, s) =>
{
var tuple = (Tuple<TimerCallback, object>)s;
tuple.Item1(tuple.Item2);
}, Tuple.Create(callback, state), CancellationToken.None,
TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnRanToCompletion,
TaskScheduler.Default);
}
public new void Dispose() { base.Cancel(); }
}
public class PCLTimer
{
private Timer _timer;
private TimeSpan _interval;
/// <summary>
/// Interval between signals in milliseconds.
/// </summary>
public double Interval
{
get { return _interval.TotalMilliseconds; }
set { _interval = TimeSpan.FromMilliseconds(value); Stop(); Start(); }
}
/// <summary>
/// True if PCLTimer is running, false if not.
/// </summary>
public bool Enabled
{
get { return null != _timer; }
set { if (value) Start(); else Stop(); }
}
/// <summary>
/// Occurs when the specified time has elapsed and the PCLTimer is enabled.
/// </summary>
public event EventHandler Elapsed;
/// <summary>
/// Starts the PCLTimer.
/// </summary>
public void Start()
{
if (0 == _interval.TotalMilliseconds)
throw new InvalidOperationException("Set Elapsed property before calling PCLTimer.Start().");
_timer = new Timer(OnElapsed, null, _interval, _interval);
}
/// <summary>
/// Stops the PCLTimer.
/// </summary>
public void Stop()
{
_timer.Dispose();
}
/// <summary>
/// Releases all resources.
/// </summary>
public void Dispose()
{
_timer.Dispose();
}
/// <summary>
/// Invokes Elapsed event.
/// </summary>
/// <param name="state"></param>
private void OnElapsed(object state)
{
if (null != _timer && null != Elapsed)
Elapsed(this, EventArgs.Empty);
}
}
}

If you interested in implementing Timer with Tasks, you can try this code:
public delegate void TimerCallback(object state);
public sealed class Timer : CancellationTokenSource, IDisposable
{
public Timer(TimerCallback callback, object state, int dueTime, int period)
{
Task.Delay(dueTime, Token).ContinueWith(async (t, s) =>
{
var tuple = (Tuple<TimerCallback, object>) s;
while (true)
{
if (IsCancellationRequested)
break;
Task.Run(() => tuple.Item1(tuple.Item2));
await Task.Delay(period);
}
}, Tuple.Create(callback, state), CancellationToken.None,
TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnRanToCompletion,
TaskScheduler.Default);
}
public new void Dispose() { base.Cancel(); }
}
As already mentioned you can introduce dependency on some interface and ask user to give you particular timer implementation.

Performing work asynchronously in .NET 4

I have legacy code which performs some very long operations on the UI thread.
What I want to do is to show a progress bar with message and run the work on another thread. Unfortunately , for now I don't have access to VS2012 so I can't use the async keyword.
I've written some code which works fine with operations of 0-1 parameters and no return value using Action.
But when I tried adjusting it to support Func I encountered some issues with
invoking the tasks and returning TResult.
Attached is my original code, would appreciate any suggestions. Thanks, Omer
public partial class FreeProgressBarFrm : System.Windows.Forms.Form
{
#region Members
/// <summary>
/// timer for the progress bar.
/// </summary>
private Timer m_Timer = new Timer();
/// <summary>
/// Delegate for the background operation to perform.
/// </summary>
private Action m_backgroundOperation;
/// <summary>
/// Standard operation to show the user while the operation is in progress.
/// </summary>
private static readonly string m_performingUpdatesMessage = IO_Global.GetResourceString("Performing updates, please wait", "Performing updates, please wait", null);
#endregion
#region Constructor
/// <summary>
/// Constructor
/// </summary>
/// <param name="backgroundDelegate"> Delegate for the background operation to perform</param>
/// <param name="operationName">meessage to show the user while the operation is in progress.</param>
public FreeProgressBarFrm(Action backgroundDelegate, string operationName)
{
InitializeComponent();
m_backgroundOperation = backgroundDelegate;
this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
this.lblOperation.Text = operationName;
m_Timer.Interval = 1000;
m_Timer.Tick += new EventHandler(m_Timer_Tick);
}
/// <summary>
/// Constructor , for progressbar with defalt user message (performing updates, please wait).
/// </summary>
/// <param name="backgroundDelegate"> Delegate for the background operation to perform</param>
/// <param name="operationName">operation display name</param>
public FreeProgressBarFrm(Action backgroundDelegate): this(backgroundDelegate, m_performingUpdatesMessage)
{
}
#endregion
#region Methods
/// <summary>
/// Call this method to begin backgorund operation while
/// showing the progress bar to the client.
/// </summary>
public void Wait()
{
ShowDialog(ControlsHelper.MainFrm);
}
/// <summary>
/// Advance the progress bar
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void m_Timer_Tick(object sender, EventArgs e)
{
PerformStep();
}
/// <summary>
/// Advance the progress bar
/// </summary>
private void PerformStep()
{
this.progressBar1.PerformStep();
this.lblOperation.Refresh();
if (this.progressBar1.Value == this.progressBar1.Maximum)
{
this.progressBar1.Value = this.progressBar1.Minimum;
}
}
/// <summary>
/// Load the form , start the progress bar and backroud task.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ProgressBarFrm_Load(object sender, EventArgs e)
{
m_Timer.Start();
this.lblOperation.Refresh();
Task task = new Task(m_backgroundOperation);
Task UITask = task.ContinueWith(delegate { OnWorkCompleted(); },
TaskScheduler.FromCurrentSynchronizationContext());
try
{
task.Start();
}
catch (Exception)
{
Close();
throw;
}
}
/// <summary>
/// Called when the work has been completed.
/// </summary>
private void OnWorkCompleted()
{
Close();
}
/// <summary>
/// Close the timer.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ProgressBarFrm_FormClosing(object sender, FormClosingEventArgs e)
{
if (m_Timer != null)
{
m_Timer.Dispose();
m_Timer = null;
}
}
#endregion
}

Here is the way i'm executing some async work,
public static class TaskExecuter
{
private static readonly ThreadLocal<List<BackgroundTask>> TasksToExecute =
new ThreadLocal<List<BackgroundTask>>(() => new List<BackgroundTask>());
public static Action<Exception> ExceptionHandler { get; set; }
public static void ExecuteLater(BackgroundTask task)
{
TasksToExecute.Value.Add(task);
}
public static void Discard()
{
TasksToExecute.Value.Clear();
}
public static void StartExecuting()
{
var value = TasksToExecute.Value;
var copy = value.ToArray();
value.Clear();
if (copy.Length > 0)
{
Task.Factory.StartNew(() =>
{
foreach (var backgroundTask in copy)
ExecuteTask(backgroundTask);
}, TaskCreationOptions.LongRunning)
.ContinueWith(task =>
{
if (ExceptionHandler != null)
ExceptionHandler(task.Exception);
}, TaskContinuationOptions.OnlyOnFaulted);
}
}
public static void ExecuteTask(BackgroundTask task)
{
task.Run();
}
}
Here is the base class
public abstract class BackgroundTask
{
protected readonly Logger Logger = LogManager.GetCurrentClassLogger();
protected virtual void Initialize()
{
}
protected virtual void OnError(Exception e)
{
//do some work
}
public bool? Run()
{
Logger.Info("Started task: {0}", GetType().Name);
Initialize();
try
{
Execute();
TaskExecuter.StartExecuting();
return true;
}
catch (Exception e)
{
Logger.ErrorException("Could not execute task " + GetType().Name, e);
OnError(e);
return false;
}
finally
{
TaskExecuter.Discard();
Logger.Info("Finished task: {0}", GetType().Name);
}
}
public abstract void Execute();
}
Here is the example of using
public class SendEmailTask : BackgroundTask
{
private const string MailServerIp = "yourip";
public string[] To { get; set; }
public string From { get; set; }
public string Template { get; set; }
public object ViewContext { get; set; }
public string[] Attachments { get; set; }
public string Subject { get; set; }
public override void Execute()
{
MailMessage message = new MailMessage();
try
{
MailAddress mailAddress = new MailAddress(From);
message.From = mailAddress;
foreach (string to in To) message.To.Add(to);
message.Subject = Subject;
if (Attachments.ReturnSuccess())
{
foreach (string attachment in Attachments)
message.Attachments.Add(new Attachment(attachment));
}
message.Priority = MailPriority.High;
message.Body = Template;
message.AlternateViews
.Add(AlternateView
.CreateAlternateViewFromString(ViewContext.ToString(), new ContentType("text/html")));
message.IsBodyHtml = true;
new SmtpClient(MailServerIp)
{
Port = 25,
UseDefaultCredentials = true
}.Send(message);
}
catch (Exception e)
{
Logger.FatalException("Error sending email:", e);
}
finally
{
message.Dispose();
}
}
public override string ToString()
{
return string.Format("To: {0}, From: {1}, Template: {2}, ViewContext: {3}, Attachments: {4}, Subject: {5}", To, From, Template, ViewContext, Attachments, Subject);
}
}
Here i've added a changed version for your needs
public static class AsyncExecuter
{
private static readonly ThreadLocal<List<Action>> TasksToExecute =
new ThreadLocal<List<Action>>(() => new List<BackgroundTask>());
public static Action<Exception> ExceptionHandler { get; set; }
public static void ExecuteLater(BackgroundTask task)
{
TasksToExecute.Value.Add(task);
}
public static void Discard()
{
TasksToExecute.Value.Clear();
}
public static void StartExecuting()
{
var value = TasksToExecute.Value;
var copy = value.ToArray();
value.Clear();
if (copy.Length > 0)
{
Task.Factory.StartNew(() =>
{
foreach (var backgroundTask in copy)
ExecuteTask(backgroundTask);
}, TaskCreationOptions.LongRunning)
.ContinueWith(task =>
{
if (ExceptionHandler != null)
ExceptionHandler(task.Exception);
}, TaskContinuationOptions.OnlyOnFaulted);
}
}
public static void ExecuteTask(Action task)
{
task.Invoke();
}
}

Class for mantain a thread safe cache

I'm developing a thread safe class that I'll use as cache, it should work in .NET and Mono.
The items have a time to live, and every time that a object is retrieved, its time to live is refreshed. Each time that I add a item, the timestamp is added to another collection that holds the same keys. A timer raises the method that looks for out dated items and remove them.
When I try to get and item, I have to provide also a delegate indicating how to obtain it if it wouldn't exist in the cache.
I've testing, and although the items removal should happen every 30 seconds in the test, it's happening very often, almost every second, and I'don't know why.
This is the class:
public class GenericCache<TId, TItem>:IDisposable where TItem : class
{
SortedDictionary<TId, TItem> _cache;
SortedDictionary<TId, DateTime> _timeouts;
Timer _timer;
Int32 _cacheTimeout;
System.Threading.ReaderWriterLockSlim _locker;
public GenericCache(Int32 minutesTTL)
{
_locker = new System.Threading.ReaderWriterLockSlim();
_cacheTimeout = minutesTTL;
_cache = new SortedDictionary<TId, TItem>();
_timeouts = new SortedDictionary<TId, DateTime>();
_timer = new Timer((minutesTTL * 60) / 2);
_timer.Elapsed += new ElapsedEventHandler(_timer_Elapsed);
_timer.AutoReset = true;
_timer.Enabled = true;
_timer.Start();
}
/// <summary>
/// Get an item, if it doesn't exist, create it using the delegate
/// </summary>
/// <param name="id">Id for the item</param>
/// <param name="create">A delegate that generates the item</param>
/// <returns>The item</returns>
public TItem Get(TId id, Func<TItem> create)
{
_locker.EnterUpgradeableReadLock();
try
{
TItem item = _cache.Where(ci => ci.Key.Equals(id)).Select(ci => ci.Value).SingleOrDefault();
if (item == null)
{
_locker.EnterWriteLock();
// check again, maybe another thread is waiting in EnterWriteLock cos the same item is null
item = _cache.Where(ci => ci.Key.Equals(id)).Select(ci => ci.Value).SingleOrDefault();
if (item == null)
{
Debug.Write("_");
item = create.Invoke();
if (item != null)
{
_cache.Add(id, item);
_timeouts.Add(id, DateTime.Now);
}
}
}
else
_timeouts[id] = DateTime.Now;
return item;
}
finally
{
if(_locker.IsWriteLockHeld)
_locker.ExitWriteLock();
_locker.ExitUpgradeableReadLock();
}
}
/// <summary>
/// Execute a delegate in the items, for example clear nested collections.
/// </summary>
/// <param name="action">The delegate</param>
public void ExecuteOnItems(Action<TItem> action)
{
_locker.EnterWriteLock();
try
{
foreach (var i in _cache.Values)
action.Invoke(i);
}
finally
{
_locker.ExitWriteLock();
}
}
/// <summary>
/// Clear this cache
/// </summary>
public void Clear()
{
_locker.EnterWriteLock();
try
{
_cache.Clear();
_timeouts.Clear();
}
finally
{
_locker.ExitWriteLock();
}
}
/// <summary>
/// Remove outdated items
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void _timer_Elapsed(object sender, ElapsedEventArgs e)
{
_locker.EnterUpgradeableReadLock();
try
{
var delete = _timeouts.Where(to => DateTime.Now.Subtract(to.Value).TotalMinutes > _cacheTimeout).ToArray();
if(delete.Any())
{
_locker.EnterWriteLock();
foreach (var timeitem in delete)
{
Debug.Write("-");
_cache.Remove(timeitem.Key);
_timeouts.Remove(timeitem.Key);
}
}
}
finally
{
if(_locker.IsWriteLockHeld)
_locker.ExitWriteLock();
_locker.ExitUpgradeableReadLock();
}
}
#region IDisposable Members
private volatile Boolean disposed = false;
protected virtual void Dispose(bool disposing)
{
if (!disposed)
{
if (disposing)
try
{
this.Clear();
}
finally
{
_locker.Dispose();
}
disposed = true;
}
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
~GenericCache()
{
Dispose(false);
}
#endregion
}
As you can see, in debug mode, when a item is added a "_" symbol is printed, and when and item is removed a "-" symbol is printed. In the tests, after the second minute can see how items are removed and added in the same second, when the items should be removed only every 30 seconds, and I don't know why:
This is how I tests:
static void Main(string[] args)
{
GenericCache<Int32, String> cache = new GenericCache<Int32, String>(1);
Debug.Listeners.Add(new ConsoleTraceListener());
Action a = delegate()
{
Random r = new Random(DateTime.Now.Millisecond);
while (true)
{
Int32 number = r.Next(0, 9999);
if (String.IsNullOrEmpty(cache.Get(number, () => number.ToString())))
Debug.Write("E");
Thread.Sleep(number);
}
};
for (int i = 0; i < 150; i++)
{
new Thread(new ThreadStart(a)).Start();
Thread.Sleep(5);
}
Console.ReadKey();
}
Do you see any problem in the GenericCache class?
Thanks in advance, kind regards.

First issue i see (assuming you are using System.Timers.Timer accepts milliseconds and you are passing seconds).
_timer = new Timer((minutesTTL * 60000) / 2);