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What happens when I reassign a frequently accessed class field to a new object?

I have a class like this:
class Test {
const int capacity = 100_0000;
private HashSet<int> set = new HashSet<int>(capacity);
public Test() { this.Reassign(); }
private void Reassign() {
var thread = new Thread(() => {
while (true) {
set = new HashSet<int>(capacity);
Thread.Sleep(10);
}
});
thread.Start();
}
public void Add(int val) {
set.Add(val);
}
}
The add method is frequently called.
var test = new Test();
Task.Run(() => {
for (int i = 0; i < 100000000; i++) {
test.Add(i);
Thread.SpinWait(5000);
}
});
It doesn't matter whether the data is successfully stored in the set, in this case, is the behavior of the add method consistent with the following code?
class LockTest {
const int capacity = 100_0000;
private HashSet<int> set = new HashSet<int>(capacity);
public LockTest() { this.Reassign(); }
private void Reassign() {
var thread = new Thread(() => {
while (true) {
lock (set) set = new HashSet<int>(capacity);
Thread.Sleep(10);
}
});
thread.Start();
}
public void Add(int val) {
lock (set) set.Add(val);
}
}
In my tests, even if there is no lock statement, there is no error. But I don't know what happens at the moment of set = new HashSet<int>(capacity);.

If you change the code to this, what do you think will happen? My guess is that the number you print out will sometimes be the same and other time different. When it is the same, lock(set) has worked, but otherwise it hasn't.
class LockTest {
const int capacity = 100_0000;
private int setCnt = 0;
private object set = new object();
public LockTest() { this.Reassign(); }
private void Reassign() {
var thread = new Thread(() => {
while (true) {
lock (set) setCnt++;
Thread.Sleep(10);
}
});
thread.Start();
}
public void Add(int val) {
lock (set) Console.WriteLine($"{setCnt}");
}
}

Cancel Task inside task when timed out. C#

I'm trying to run collection of tasks. I have a procesing object model, which properties I don't know. That's is why I've created a child of this class. I have a collection of ProcesingTask objects. This is my code:
public sealed class ProcessingTask : ProcessingObject
{
private CancellationTokenSource cancelToken;
private System.Timers.Timer _timer;
public int TimeOut {private get; set; }
public int ProcessObjectID { get; private set; }
public Task ProcessObjectTask { get; private set; }
public QueueObject queueObject { private get; set; }
public ProcessingTask(int processObjectID)
{
this.ProcessObjectID = processObjectID;
ResetTask();
}
private void InitialTimeOut()
{
_timer = new System.Timers.Timer(TimeOut);
_timer.Elapsed += new ElapsedEventHandler(TimedOut);
_timer.Enabled = true;
}
private void TimedOut(object sender, ElapsedEventArgs e)
{
cancelToken.Cancel();
Console.WriteLine("Thread {0} was timed out...", ProcessObjectID);
_timer.Stop();
}
public void ResetTask()
{
cancelToken = new CancellationTokenSource();
ProcessObjectTask = new Task(() => DoTaskWork(), cancelToken.Token);
}
public void DoTaskWork()
{
InitialTimeOut();
Random rand = new Random();
int operationTime = rand.Next(2000, 20000);
Thread.Sleep(operationTime);
_timer.Stop();
Console.WriteLine("Thread {0} was finished...", ProcessObjectID);
}
}
public class CustomThreadPool
{
private IList<ProcessingTask> _processingTasks;
public CustomThreadPool(List<ProcessingTask> processingObjects)
{
this._processingTasks = processingObjects;
}
public void RunThreadPool(Queue<QueueObject> queue, int batchSize)
{
for (int i = 1; i <= batchSize; i++)
{
QueueObject queueObject = queue.ToArray().ToList().FirstOrDefault();
ProcessingTask task = _processingTasks.FirstOrDefault(x => x.ProcessObjectID == queueObject.QueueObjectId);
task.queueObject = queue.Dequeue();
task.TimeOut = 3000;
task.ProcessObjectTask.Start();
}
}
public void WaitAll()
{
var tasks = _processingTasks.Select(x => x.ProcessObjectTask).ToArray();
Task.WaitAll(tasks);
}
}
I need to stop DoTaskWork() if running time was timed out. I'm trying to use timer and CancellationToken. But DoTaskWork() still doing his job after TimedOut(). Is any way to resolve this issue?

Though you send the cancel signal, you don't do anything with that in DoTaskWork
public void DoTaskWork()
{
InitialTimeOut();
Random rand = new Random();
int operationTime = rand.Next(2000, 20000);
// Thread.Sleep(operationTime); // this imitates a non-responsive operation
// but this imitates a responsive operation:
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
while (!cancelToken.IsCancellationRequested
&& stopwatch.ElapsedMilliseconds < operationTime)
{
Thread.Sleep(10);
}
_timer.Stop();
Console.WriteLine("Thread {0} was finished...", ProcessObjectID);
}

You have to implement your method DoTaskWork() accordingly.
Assume this as a sample. I am assuming that your thead is doing some continuos work rather just sleep. Otherwise you can use abort method which will just abort the thread even if its in sleep mode.
public void DoTaskWork()
{
InitialTimeOut();
Random rand = new Random();
int operationTime = rand.Next(2000, 20000);
while (true)
{
if (cancelToken.IsCancellationRequested)
{
throw new Exception("Cancellation requested.");
}
Thread.Sleep(operationTime);
}
_timer.Stop();
Console.WriteLine("Thread {0} was finished...", ProcessObjectID);
}

Set maximum value for the progress bar to match length of queue.

I would like to visualize how a queue when accessed by two reader threads and a writer thread grows and shrinks, with help of a progressbar in mainform. I will use a delegate to invoke the progress bar in main form and set its value to Queue.Value ( Toys.lenght). The progressbar does not behave as stated, it does not grow all the way and the lenght variables does not either.
public class Buffer
{
private delegate void Display(int v, ProgressBar f );
private Queue<Toy> Toys = new Queue<Toy>();
private object MyLock = new object();
private int max;
private int lenght;
private ProgressBar progressbar1;
public Buffer(ProgressBar r)
{
this.progressbar1 = r;
this.max = 10;
this.lenght = Toys.Count;
}
public void writeMethod(Toy toy)
{
lock (MyLock)
{
if (Toys.Count == max)
{
Monitor.Wait(MyLock);
}
Toys.Enqueue(toy);
Monitor.PulseAll(MyLock);
progressbar1.Invoke(new Display(Disp), new object[] {Toys.Count, progressbar1});
MessageBox.Show("Que contains these items" + lenght);
}
}
public void readMethod()
{
lock (MyLock)
{
if(Toys.Count == 0)
{
Monitor.Wait(MyLock);
}
Toys.Dequeue();
Monitor.PulseAll(MyLock);
}
}
public void Disp(int I, ProgressBar l)
{
progressbar1.Value = I;
}
}
}

Double check the variable lenght, use count instead. Change Progressbar default setting for maximum size from 100 to 10 to match size of the queue Toys. In Disp method change from = I to += I;
{
public class Buffer
{
private delegate void Display(int v, ProgressBar f );
private Queue<Toy> Toys = new Queue<Toy>();
private object MyLock = new object();
private int max;
private int lenght;
private ProgressBar progressbar1;
public Buffer(ProgressBar r)
{
this.progressbar1 = r;
this.max = 10;
this.lenght = Toys.Count;
}
public void writeMethod(Toy toy)
{
lock (MyLock)
{
if (Toys.Count >= max)
{
Monitor.Wait(MyLock);
}
if(Toys.Count <= max)
{
Toys.Enqueue(toy);
progressbar1.Invoke(new Display(Disp), new object[] {Toys.Count, progressbar1});
}
Monitor.PulseAll(MyLock);
MessageBox.Show("Que contains these items" + Toys.Count);
}
}
public void readMethod()
{
lock (MyLock)
{
if(Toys.Count == 0)
{
Monitor.Wait(MyLock);
}
Toys.Dequeue();
Monitor.PulseAll(MyLock);
}
}
public void Disp(int I, ProgressBar l)
{
progressbar1.Value += I;
}
}
}

Signaling threads to stop

have such code.
Start threads:
Thread[] thr;
static object locker = new object();
bool liking = true;
private void button2_Click(object sender, EventArgs e)
{
button2.Enabled = false;
button3.Enabled = true;
string post = create_note();
decimal value = Program.Data.numericUpDown1;
int i = 0;
int j = (int)(value);
thr = new Thread[j];
for (; i < j; i++)
{
thr[i] = new Thread(() => invite(post));
thr[i].IsBackground = true;
thr[i].Start();
}
}
public void invite(string post)
{
while (liking)
{
if (//some comdition)
exit all threads, and start string post = create_note(); again
}
}
If some condition in invite(string post) comes true I need to stop all threads, and go to string post = create_note(); again, get string post and start threads again.
How to do it?

Instead of manual thread management, use Parallel.For with CancellationToken:
var cts = new CancellationTokenSource();
var options = new ParallelOptions
{
CancellationToken = cts.Token,
MaxDegreeOfParallelism = System.Environment.ProcessorCount
};
var result = Parallel.For(0, j, options, i =>
{
invite(post);
options.CancellationToken.ThrowIfCancellationRequested();
});
When you want to cancel parallel calculations, just call cts.Cancel() from external code.

You can use lock and create a class that manage your threads like that :
public class SyncClass
{
public Thread[] thr;
private int NumberOfWorkingThreads { get; set; }
private object Sync = new object();
public int ThreadNumber { get; private set; }
public event EventHandler TasksFinished;
public SyncClass(int threadNumber)
{
thr = new Thread[threadNumber];
ThreadNumber = threadNumber;
NumberOfWorkingThreads = ThreadNumber;
//LunchThreads(threadNumber);
}
protected void OnTasksFinished()
{
if (TasksFinished == null)
return;
lock (Sync)
{
NumberOfWorkingThreads--;
if (NumberOfWorkingThreads == 0)
TasksFinished(this, new EventArgs());
}
}
public void LunchThreads()
{
string post = create_note();
for (int i = 0; i < ThreadNumber; i++)
{
thr[i] = new Thread(() => invite(post));
thr[i].IsBackground = true;
thr[i].Start();
}
}
private void invite(string post)
{
while (true)
{
if (true)
{
break;
}
}
OnTasksFinished();
}
}
Use the event to notify the end of all threads then the class will be used like that:
private void Operation()
{
var sync = new SyncClass(10);
sync.TasksFinished += sync_TasksFinished;
sync.LunchThreads();
}
void sync_TasksFinished(object sender, EventArgs e)
{
Operation();
}

Help with synchronization from a unit test in C#

I'm testing a class that wraps BackgroundWorker to perform an operation away from the UI thread in my application.
The test below fails if Timeout is exceeded and passes if progressEventCount reaches the expected number of events before then.
My question is about synchronization. asyncExecutor.Progressed is fired from the Thread Pool thread that BackgroundWorker is using and the test thread reads it back in the while loop.
Am I using lock correctly?
[Test]
[Timeout(1250)]
public void Execute()
{
var locker = new object();
const int numberOfEvents = 10;
const int frequencyOfEvents = 100;
var start = DateTime.Now;
int progressEventCount = 0;
IGradualOperation tester = new TestGradualOperation(numberOfEvents, frequencyOfEvents);
var asyncExecutor = new AsynchronousOperationExecutor();
asyncExecutor.Progressed += (s, e) => { lock (locker) progressEventCount++; };
asyncExecutor.Execute(tester);
while (true)
{
int count;
lock (locker)
{
count = progressEventCount;
}
if (count < numberOfEvents) continue;
Assert.Pass("Succeeded after {0} milliseconds", (DateTime.Now - start).TotalMilliseconds);
}
}
// Implementation
public class AsynchronousOperationExecutor
{
public void Execute(IGradualOperation gradualOperation)
{
var backgroundWorker = new BackgroundWorker {WorkerReportsProgress = true};
backgroundWorker.DoWork += BackgroundWorkerDoWork;
backgroundWorker.ProgressChanged += BackgroundWorkerProgressChanged;
backgroundWorker.RunWorkerAsync(gradualOperation);
}
private void BackgroundWorkerProgressChanged(object sender, ProgressChangedEventArgs e)
{
var myArgs = e.UserState as ProgressEventArgs;
OnProgressed(myArgs);
}
static void BackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
var workerThis = sender as BackgroundWorker;
var operation = e.Argument as IGradualOperation;
if (workerThis == null || operation == null) return;
operation.Progressed += (s, e1) => workerThis.ReportProgress((int)e1.Percentage, e1);
operation.Run();
}
private void OnProgressed(ProgressEventArgs e)
{
if (Progressed != null)
Progressed(this, e);
}
public event EventHandler<ProgressEventArgs> Progressed;
}
// Test Helper Class
public class TestGradualOperation : IGradualOperation
{
private readonly int _numberOfEvents;
private readonly int _frequencyMilliseconds;
public TestGradualOperation(int numberOfEvents, int frequencyMilliseconds)
{
_numberOfEvents = numberOfEvents;
_frequencyMilliseconds = frequencyMilliseconds;
}
public void Run()
{
for (int i = 0; i < _numberOfEvents; i++)
{
Thread.Sleep(_frequencyMilliseconds);
OnProgressed(new ProgressEventArgs(i, _numberOfEvents));
}
}
private void OnProgressed(ProgressEventArgs e)
{
if (Progressed != null)
Progressed(this, e);
}
public event EventHandler<ProgressEventArgs> Progressed;
}

I think this revision is an improvement, blocking the test thread and signalling with an AutoResetEvent. Not winning any brownie points for test readability though.
[Test]
[Timeout(1250)]
public void Execute()
{
var locker = new object();
EventWaitHandle waitHandle = new AutoResetEvent(false);// <--
const int numberOfEvents = 10;
const int frequencyOfEvents = 100;
var start = DateTime.Now;
int progressEventCount = 0;
IGradualOperation tester = new TestGradualOperation(numberOfEvents, frequencyOfEvents);
var asyncExecutor = new AsynchronousOperationExecutor();
asyncExecutor.Progressed += (s, e) =>
{
lock (locker)
{
progressEventCount++;
waitHandle.Set();// <--
}
};
asyncExecutor.Execute(tester);
while (true)
{
waitHandle.WaitOne();// <--
if (progressEventCount < numberOfEvents) continue;
Assert.Pass("Succeeded after {0} milliseconds", (DateTime.Now - start).TotalMilliseconds);
}
}