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Changing thread context in C# console application

I have a C# console app in which I can get, among other things, input via a TCP socket connection. How do I switch to the main thread when I receive an input via the receive function over the socket?
So similar to something like this in WPF:
public void TaskDispatcher()
{
if (DispatcherObjectForTaskDispatcher.Thread != System.Threading.Thread.CurrentThread)
DispatcherObjectForTaskDispatcher.Invoke(new TaskDispatcherDelegate(TaskDispatcher));
else
{
// Do some thing in the UI thread
}
}

Just use a Producer-Consumer pattern as in the working example below. Enqueue jobs from other threads and let the main thread process the queued jobs from a job queue.
I used a timer thread and a user input thread to simulate 2 threads producing jobs. You could implement your TCP events to just enqueue a job in the job queue. You should store any relevant objects as arguments inside your job, for later processing. You must also define a function to be called by the job, which will run in the main thread.
The main thread is used here just for dequeueing jobs and processing them, but you could use any other thread for this purpose if you improve this code a little bit.
You could even implement multi-threading processing, on which more processing threads dequeue from the same job queue. Be aware this brings new concurrency problems which you may have to deal with. That's the drawback for gaining much more processing power in your application. Some scenarios are suitable for multi-threading processing (e.g. video / image processing) while some others are not.
The code below is a full working example written in a Visual Studio 2017, DotNET 4.6.1, console application project. Just copy, paste, and hit F5.
using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Threading;
// Compiled and tested in: Visual Studio 2017, DotNET 4.6.1
namespace MyNamespace
{
public class Program
{
public static void Main(string[] args)
{
MyApplication app = new MyApplication();
app.Run();
}
}
public class MyApplication
{
private BlockingCollection<Job> JobQueue = new BlockingCollection<Job>();
private CancellationTokenSource JobCancellationTokenSource = new CancellationTokenSource();
private CancellationToken JobCancellationToken;
private Timer Timer;
private Thread UserInputThread;
public void Run()
{
// Give a name to the main thread:
Thread.CurrentThread.Name = "Main";
// Fires a Timer thread:
Timer = new Timer(new TimerCallback(TimerCallback), null, 1000, 2000);
// Fires a thread to read user inputs:
UserInputThread = new Thread(new ThreadStart(ReadUserInputs))
{
Name = "UserInputs",
IsBackground = true
};
UserInputThread.Start();
// Prepares a token to cancel the job queue:
JobCancellationToken = JobCancellationTokenSource.Token;
// Start processing jobs:
ProcessJobs();
// Clean up:
JobQueue.Dispose();
Timer.Dispose();
UserInputThread.Abort();
Console.WriteLine("Done.");
}
private void ProcessJobs()
{
try
{
// Checks if the blocking collection is still up for dequeueing:
while (!JobQueue.IsCompleted)
{
// The following line blocks the thread until a job is available or throws an exception in case the token is cancelled:
JobQueue.Take(JobCancellationToken).Run();
}
}
catch { }
}
private void ReadUserInputs()
{
// User input thread is running here.
ConsoleKey key = ConsoleKey.Enter;
// Reads user inputs and queue them for processing until the escape key is pressed:
while ((key = Console.ReadKey(true).Key) != ConsoleKey.Escape)
{
Job userInputJob = new Job("UserInput", this, new Action<ConsoleKey>(ProcessUserInputs), key);
JobQueue.Add(userInputJob);
}
// Stops processing the JobQueue:
JobCancellationTokenSource.Cancel();
}
private void ProcessUserInputs(ConsoleKey key)
{
// Main thread is running here.
Console.WriteLine($"You just typed '{key}'. (Thread: {Thread.CurrentThread.Name})");
}
private void TimerCallback(object param)
{
// Timer thread is running here.
Job job = new Job("TimerJob", this, new Action<string>(ProcessTimer), "A job from timer callback was processed.");
JobQueue.TryAdd(job); // Just enqueues the job for later processing
}
private void ProcessTimer(string message)
{
// Main thread is running here.
Console.WriteLine($"{message} (Thread: {Thread.CurrentThread.Name})");
}
}
/// <summary>
/// The Job class wraps an object's method call, with or without arguments. This method is called later, during the Job execution.
/// </summary>
public class Job
{
public string Name { get; }
private object TargetObject;
private Delegate TargetMethod;
private object[] Arguments;
public Job(string name, object obj, Delegate method, params object[] args)
{
Name = name;
TargetObject = obj;
TargetMethod = method;
Arguments = args;
}
public void Run()
{
try
{
TargetMethod.Method.Invoke(TargetObject, Arguments);
}
catch(Exception ex)
{
Debug.WriteLine($"Unexpected error running job '{Name}': {ex}");
}
}
}
}

Thread Safety in Concurrent Queue C#

I have a MessagesManager thread to which different threads may send messages and then this MessagesManager thread is responsible to publish these messages inside SendMessageToTcpIP() (start point of MessagesManager thread ).
class MessagesManager : IMessageNotifier
{
//private
private readonly AutoResetEvent _waitTillMessageQueueEmptyARE = new AutoResetEvent(false);
private ConcurrentQueue<string> MessagesQueue = new ConcurrentQueue<string>();
public void PublishMessage(string Message)
{
MessagesQueue.Enqueue(Message);
_waitTillMessageQueueEmptyARE.Set();
}
public void SendMessageToTcpIP()
{
//keep waiting till a new message comes
while (MessagesQueue.Count() == 0)
{
_waitTillMessageQueueEmptyARE.WaitOne();
}
//Copy the Concurrent Queue into a local queue - keep dequeuing the item once it is inserts into the local Queue
Queue<string> localMessagesQueue = new Queue<string>();
while (!MessagesQueue.IsEmpty)
{
string message;
bool isRemoved = MessagesQueue.TryDequeue(out message);
if (isRemoved)
localMessagesQueue.Enqueue(message);
}
//Use the Local Queue for further processing
while (localMessagesQueue.Count() != 0)
{
TcpIpMessageSenderClient.ConnectAndSendMessage(localMessagesQueue.Dequeue().PadRight(80, ' '));
Thread.Sleep(2000);
}
}
}
The different threads (3-4) send their message by calling the PublishMessage(string Message) (using same object to MessageManager). Once the message comes, I push that message into a concurrent queue and notifies the SendMessageToTcpIP() by setting _waitTillMessageQueueEmptyARE.Set();. Inside SendMessageToTcpIP(), I am copying the message from the concurrent queue inside a local queue and then publish one by one.
QUESTIONS: Is it thread safe to do enqueuing and dequeuing in this way? Could there be some strange effects due to it?

While this is probably thread-safe, there are built-in classes in .NET to help with "many publishers one consumer" pattern, like BlockingCollection. You can rewrite your class like this:
class MessagesManager : IDisposable {
// note that your ConcurrentQueue is still in play, passed to constructor
private readonly BlockingCollection<string> MessagesQueue = new BlockingCollection<string>(new ConcurrentQueue<string>());
public MessagesManager() {
// start consumer thread here
new Thread(SendLoop) {
IsBackground = true
}.Start();
}
public void PublishMessage(string Message) {
// no need to notify here, will be done for you
MessagesQueue.Add(Message);
}
private void SendLoop() {
// this blocks until new items are available
foreach (var item in MessagesQueue.GetConsumingEnumerable()) {
// ensure that you handle exceptions here, or whole thing will break on exception
TcpIpMessageSenderClient.ConnectAndSendMessage(item.PadRight(80, ' '));
Thread.Sleep(2000); // only if you are sure this is required
}
}
public void Dispose() {
// this will "complete" GetConsumingEnumerable, so your thread will complete
MessagesQueue.CompleteAdding();
MessagesQueue.Dispose();
}
}

.NET already provides ActionBlock< T> that allows posting messages to a buffer and processing them asynchronously. By default, only one message is processed at a time.
Your code could be rewritten as:
//In an initialization function
ActionBlock<string> _hmiAgent=new ActionBlock<string>(async msg=>{
TcpIpMessageSenderClient.ConnectAndSendMessage(msg.PadRight(80, ' '));
await Task.Delay(2000);
);
//In some other thread ...
foreach ( ....)
{
_hmiAgent.Post(someMessage);
}
// When the application closes
_hmiAgent.Complete();
await _hmiAgent.Completion;
ActionBlock offers many benefits - you can specify a limit to the number of items it can accept in a buffer and specify that multiple messages can be processed in parallel. You can also combine multiple blocks in a processing pipeline. In a desktop application, a message can be posted to a pipeline in response to an event, get processed by separate blocks and results posted to a final block that updates the UI.
Padding, for example, could be performed by an intermediary TransformBlock< TIn,TOut>. This transformation is trivial and the cost of using the block is greater than the method, but that's just an illustration:
//In an initialization function
TransformBlock<string> _hmiAgent=new TransformBlock<string,string>(
msg=>msg.PadRight(80, ' '));
ActionBlock<string> _tcpBlock=new ActionBlock<string>(async msg=>{
TcpIpMessageSenderClient.ConnectAndSendMessage());
await Task.Delay(2000);
);
var linkOptions=new DataflowLinkOptions{PropagateCompletion = true};
_hmiAgent.LinkTo(_tcpBlock);
The posting code doesn't change at all
_hmiAgent.Post(someMessage);
When the application terminates, we need to wait for the _tcpBlock to complete:
_hmiAgent.Complete();
await _tcpBlock.Completion;
Visual Studio 2015+ itself uses TPL Dataflow for such scenarios
Bar Arnon provides a better example in TPL Dataflow Is The Best Library You're Not Using, that shows how both synchronous and asynchronous methods can be used in a block.

The code is thread safe since both ConcurrentQueue and AutoResetEvent are thread safe. your strings are anyway being read and never being written to, so this code is thread safe.
However, You have to make sure you call SendMessageToTcpIP in some sort of a loop.
otherwise , you have a dangerous race condition - some messages may get lost:
while (!MessagesQueue.IsEmpty)
{
string message;
bool isRemoved = MessagesQueue.TryDequeue(out message);
if (isRemoved)
localMessagesQueue.Enqueue(message);
}
//<<--- what happens if another thread enqueues a message here?
while (localMessagesQueue.Count() != 0)
{
TcpIpMessageSenderClient.ConnectAndSendMessage(localMessagesQueue.Dequeue().PadRight(80, ' '));
Thread.Sleep(2000);
}
Other than that, AutoResetEvent is extremely heavy object. it uses a kernel object to synchronize threads. every call is a system call which may be costly. consider using user mode synchronization object (doesn't .net provides some sort of condition variable?)

This is an refactored code snippet of how I would implement this functionality:
class MessagesManager {
private readonly AutoResetEvent messagesAvailableSignal = new AutoResetEvent(false);
private readonly ConcurrentQueue<string> messageQueue = new ConcurrentQueue<string>();
public void PublishMessage(string Message) {
messageQueue.Enqueue(Message);
messagesAvailableSignal.Set();
}
public void SendMessageToTcpIP() {
while (true) {
messagesAvailableSignal.WaitOne();
while (!messageQueue.IsEmpty) {
string message;
if (messageQueue.TryDequeue(out message)) {
TcpIpMessageSenderClient.ConnectAndSendMessage(message.PadRight(80, ' '));
}
}
}
}
}
Points to note here:
This drains the queue completely: if there is at least one message, it will process all of them
The 2000ms Thread sleep is removed

How to stop a thread if thread takes too long

I have a situation that i export data to a file and what i have been asked to do is to provide a cancel button which on click will stop the export if it takes too much time to export.
I started exporting to the file in a thread. And i try to abort the thread on the button click. But it do not work.
I searched on Google and i found that abort() is not recommended. But what else should I choose to achieve it?
My current code is:
private void ExportButtonClick(object param)
{
IList<Ur1R2_Time_Points> data = ct.T_UR.ToList();
DataTable dtData = ExportHelper.ToDataTable(data);
thread = new Thread(new ThreadStart(()=>ExportHelper.DataTableToCsv(dtData, "ExportFile.csv")));
thread.SetApartmentState(ApartmentState.STA);
thread.IsBackground = true;
thread.Name = "PDF";
thread.Start();
}
private void StopButtonClick(object param)
{
if (thread.Name == "PDF")
{
thread.Interrupt();
thread.Abort();
}
}

Aborting a thread is a bad idea, especially when dealing with files. You won't have a chance to clean up half-written files or clean-up inconsistent state.
It won't harm the .NET Runtime bat it can hurt your own application eg if the worker method leaves global state, files or database records in an inconsistent state.
It's always preferable to use cooperative cancellation - the thread periodically checks a coordination construct like a ManualResetEvent or CancellationToken. You can't use a simple variable like a Boolean flag, as this can lead to race conditions, eg if two or more threads try to set it at the same time.
You can read about cancellation in .NET in the Cancellation in Managed Threads section of MSDN.
The CancellationToken/CancellationTokenSource classes were added in .NET 4 to make cancellation easier that passing around events.
In your case, you should modify your DataTableToCsv to accept a CancellationToken. That token is generated by a CancellationTokenSource class.
When you call CancellationTokenSource.Cancel the token's IsCancellationRequested property becomes true. Your DataTableToCsv method should check this flag periodically. If it's set, it should exit any loops, delete any inconsistent files etc.
Timeouts are directly supported with CancelAfter. Essentially, CancelAfter starts a timer that will fire Cancel when it expires.
Your code could look like this:
CancellationTokenSource _exportCts = null;
private void ExportButtonClick(object param)
{
IList<Ur1R2_Time_Points> data = ct.T_UR.ToList();
DataTable dtData = ExportHelper.ToDataTable(data);
_exportCts=new CancellationTokenSource();
var token=_exportCts.Token;
thread = new Thread(new ThreadStart(()=>
ExportHelper.DataTableToCsv(dtData, "ExportFile.csv",token)));
thread.SetApartmentState(ApartmentState.STA);
thread.IsBackground = true;
thread.Name = "PDF";
_exportCts.CancelAfter(10000);
thread.Start();
}
private void StopButtonClick(object param)
{
if (_exportCts!=null)
{
_exportCts.Cancel();
}
}
DataTableToCsv should contain code similar to this:
foreach(var row in myTable)
{
if (token.IsCancellationRequested)
{
break;
}
//else continue with processing
var line=String.Join(",", row.ItemArray);
writer.WriteLine(line);
}
You can clean up your code quite a bit by using tasks instead of raw threads:
private async void ExportButtonClick(object param)
{
IList<Ur1R2_Time_Points> data = ct.T_UR.ToList();
DataTable dtData = ExportHelper.ToDataTable(data);
_exportCts=new CancellationTokenSource();
var token=_exportCts.Token;
_exportCts.CancelAfter(10000);
await Task.Run(()=> ExportHelper.DataTableToCsv(dtData, "ExportFile.csv",token)));
MessageBox.Show("Finished");
}
You could also speed it up by using asynchronous operations, eg to read data from the database or write to text files without blocking or using threads. Windows IO (both file and network) is asynchronous at the driver level. Methods like File.WriteLineAsync don't use threads to write to a file.
Your Export button handler could become :
private void ExportButtonClick(object param)
{
IList<Ur1R2_Time_Points> data = ct.T_UR.ToList();
DataTable dtData = ExportHelper.ToDataTable(data);
_exportCts=new CancellationTokenSource();
var token=_exportCts.Token;
_exportCts.CancelAfter(10000);
await Task.Run(async ()=> ExportHelper.DataTableToCsv(dtData, "ExportFile.csv",token)));
MessageBox.Show("Finished");
}
and DataTableToCsv :
public async Task DataTableToCsv(DataTable table, string file,CancellationToken token)
{
...
foreach(var row in myTable)
{
if (token.IsCancellationRequested)
{
break;
}
//else continue with processing
var line=String.Join(",", row.ItemArray);
await writer.WriteLineAsync(line);
}

You can use a boolean flag. Use a volatile boolean for that.
In the helper do something like:
this.aborted = false;
while(!finished && !aborted) {
//process one row
}
Whenever you want to cancel the operation, you call a method to set aborted to true:
public void Abort() {
this.aborted = true;
}

Have a read here: https://msdn.microsoft.com/en-us/library/system.threading.threadabortexception(v=vs.110).aspx
When a call is made to the Abort method to destroy a thread, the common language runtime throws a ThreadAbortException. ThreadAbortException is a special exception that can be caught, but it will automatically be raised again at the end of the catch block. When this exception is raised, the runtime executes all the finally blocks before ending the thread. Because the thread can do an unbounded computation in the finally blocks or call Thread.ResetAbort to cancel the abort, there is no guarantee that the thread will ever end. If you want to wait until the aborted thread has ended, you can call the Thread.Join method. Join is a blocking call that does not return until the thread actually stops executing.
Since Thread.Abort() is executed by another thread, it can happen anytime and when it happens ThreadAbortException is thrown on target thread.
Inside ExportHelper.DataTableToCsv:
catch(ThreadAbortException e) {
Thread.ResetAbort();
}
On StopButtonClick
if (thread.Name == "PDF")
{
thread.Interrupt();
thread.Join();
}

To Stop a thread you have one option of Thread.Abort.However because this method thrown ThreadAbortException on the target thread when it executed by another thead.
Which is not recommended.
The second option to stop a thread is by using shared variable that both your target and your calling thread can access.
See the Example ::
public static class Program
{
public static void ThreadMethod(object o)
{
for (int i = 0; i < (int)o; i++)
{
Console.WriteLine("ThreadProc: { 0}", i);
Thread.Sleep(0);
}
}
public static void Main()
{
bool stopped = false;
Thread t = new Thread(new ThreadStart(() =>
{
while (!stopped)
{
Console.WriteLine("Running...");
Thread.Sleep(1000);
}
}));
t.Start();
Console.WriteLine("Press any key to exit");
Console.ReadKey();
stopped = true;
t.Join();
}
}
//Source :: Book --> Programming in c#

Stopping a Thread, ManualResetEvent, volatile boolean or cancellationToken

I have a Thread (STAThread) in a Windows Service, which performs a big amount of work. When the windows service is restarted I want to stop this thread gracefully.
I know of a couple of ways
A volatile boolean
ManualResetEvent
CancellationToken
As far as I have found out Thread.Abort is a no go...
What is the best practice ?
The work is perfomed in another class than the one where the thread is started, so it is necessary to either introduce a cancellationToken parameter in a constructor or for example have a volatile variable. But I just can't figure out what is smartest.
Update
Just to clarify a little I have wrapped up a very simple example of what I'm talking about. As said earlier, this is being done in a windows service. Right now I'm thinking a volatile boolean that is checked on in the loop or a cancellationToken....
I cannot wait for the loop to finish, as stated below it can take several minutes, making the system administrators of the server believe that something is wrong with the service when they need to restart it.... I can without problems just drop all the work within the loop without problems, however I cannot do this with a Thread.Abort it is "evil" and furthermore a COM interface is called, so a small clean up is needed.
Class Scheduler{
private Thread apartmentThread;
private Worker worker;
void Scheduling(){
worker = new Worker();
apartmentThread = new Thread(Run);
apartmentThread.SetApartmentState(ApartmentState.STA);
apartmentThread.Start();
}
private void Run() {
while (!token.IsCancellationRequested) {
Thread.Sleep(pollInterval * MillisecondsToSeconds);
if (!token.IsCancellationRequested) {
worker.DoWork();
}
}
}
}
Class Worker{
//This will take several minutes....
public void DoWork(){
for(int i = 0; i < 50000; i++){
//Do some work including communication with a COM interface
//Communication with COM interface doesn't take long
}
}
}
UPDATE
Just examined performance, using a cancellationToken where the isCancelled state is "examined" in the code, is much faster than using a waitOne on a ManualResetEventSlim. Some quick figuers, an if on the cancellationToken iterating 100.000.000 times in a for loop costs me approx. 500 ms, where the WaitOne costs approx. 3 seconds. So performance in this scenario it is faster to use the cancellationToken.

You haven't posted enough of your implementation but I would highly recommend a CancellationToken if that is available to you. It's simple enough to use and understand from a maintainability standpoint. You can setup cooperative cancellation as well too if you decide to have more than one worker thread.
If you find yourself in a situation where this thread may block for long periods of time, it's best to setup your architecture so that this doesn't occur. You shouldn't be starting threads that won't play nice when you tell them to stop. If they don't stop when you ask them, the only real way is to tear down the process and let the OS kill them.
Eric Lippert posted a fantastic answer to a somewhat-related question here.

I tend to use a bool flag, a lock object and a Terminate() method, such as:
object locker = new object();
bool do_term = false;
Thread thread = new Thread(ThreadStart(ThreadProc));
thread.Start();
void ThreadProc()
{
while (true) {
lock (locker) {
if (do_term) break;
}
... do work...
}
}
void Terminate()
{
lock (locker) {
do_term = true;
}
}
Asides from Terminate() all the other fields and methods are private to the "worker" class.

Use a WaitHandle, most preferably a ManualResetEvent. Your best bet is to let whatever is in your loop finish. This is the safest way to accomplish your goal.
ManualResetEvent _stopSignal = new ManualResetEvent(false); // Your "stopper"
ManualResetEvent _exitedSignal = new ManualResetEvent(false);
void DoProcessing() {
try {
while (!_stopSignal.WaitOne(0)) {
DoSomething();
}
}
finally {
_exitedSignal.Set();
}
}
void DoSomething() {
//Some work goes here
}
public void Terminate() {
_stopSignal.Set();
_exitedSignal.WaitOne();
}
Then to use it:
Thread thread = new Thread(() => { thing.DoProcessing(); });
thread.Start();
//Some time later...
thing.Terminate();
If you have a particularly long-running process in your "DoSomething" implementation, you may want to call that asynchronously, and provide it with state information. That can get pretty complicated, though -- better to just wait until your process is finished, then exit, if you are able.

There are two situations in which you may find your thread:
Processing.
Blocking.
In the case where your thread is processing something, you must wait for your thread to finish processing in order for it to safely exit. If it's part of a work loop, then you can use a boolean flag to terminate the loop.
In the case where your thread is blocking, then you need to wake your thread and get it processing again. A thread may be blocking on a ManualResetEvent, a database call, a socket call or whatever else you could block on. In order to wake it up, you must call the Thread.Interrupt() method which will raise a ThreadInterruptedException.
It may look something like this:
private object sync = new object():
private bool running = false;
private void Run()
{
running = true;
while(true)
{
try
{
lock(sync)
{
if(!running)
{
break;
}
}
BlockingFunction();
}
catch(ThreadInterruptedException)
{
break;
}
}
}
public void Stop()
{
lock(sync)
{
running = false;
}
}
And here is how you can use it:
MyRunner r = new MyRunner();
Thread t = new Thread(()=>
{
r.Run();
});
t.IsBackground = true;
t.Start();
// To stop the thread
r.Stop();
// Interrupt the thread if it's in a blocking state
t.Interrupt();
// Wait for the thread to exit
t.Join();

Object synchronization method was called from an unsynchronized block of code. Exception on Mutex.Release()

I have found different articles about this exception but none of them was my case.
Here is the source code:
class Program
{
private static Mutex mutex;
private static bool mutexIsLocked = false;
static void Main(string[] args)
{
ICrmService crmService =
new ArmenianSoftware.Crm.Common.CrmServiceWrapper(GetCrmService("Armsoft", "crmserver"));
//Lock mutex for concurrent access to workflow
mutex = new Mutex(true, "ArmenianSoftware.Crm.Common.FilterCtiCallLogActivity");
mutexIsLocked = true;
//Create object for updating filtered cti call log
ArmenianSoftware.Crm.Common.FilterCtiCallLog filterCtiCallLog =
new ArmenianSoftware.Crm.Common.FilterCtiCallLog(crmService);
//Bind events
filterCtiCallLog.CtiCallsRetrieved += new EventHandler<ArmenianSoftware.Crm.Common.CtiCallsRetrievedEventArgs>(filterCtiCallLog_CtiCallsRetrieved);
//Execute filter
try
{
filterCtiCallLog.CreateFilteredCtiCallLogSync();
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (mutexIsLocked)
{
mutexIsLocked = false;
mutex.ReleaseMutex();
}
}
}
static void filterCtiCallLog_CtiCallsRetrieved(object sender,
ArmenianSoftware.Crm.Common.CtiCallsRetrievedEventArgs e)
{
tryasasas
{
if (mutexIsLocked)
{
mutexIsLocked = false;
mutex.ReleaseMutex();
}
}
catch (Exception ex)
{
throw ex;
}
}
}
filterCtiCallLog.CreateFilteredCtiCallLogSync(); function executes requests to server, and raises some events, one of which is CtiCallsRetrieve event. And I need to release the mutex when this event is fired. But on calling the mutex.Release() function exception is thrown. CreateFilteredCtiCallLogSync works synchronously. What is the problem?

Keeping a bool around that indicates that the mutex is owned is a grave mistake. You are not making the bool thread-safe. You got into this pickle because you are using the wrong synchronization object. A mutex has thread-affinity, the owner of a mutex is a thread. The thread that acquired it must also be the one that calls ReleaseMutex(). Which is why your code bombs.
You in all likelihood need an event here, use AutoResetEvent. Create it in the main thread, call Set() in the worker, WaitOne() in the main thread to wait for the worker to complete its job. And dispose it afterwards. Also note that using a thread to perform a job and having your main thread wait for its completion is not productive. You might as well have the main thread do the job.
If you are actually doing this to protect access to an object that's not thread-safe (it isn't clear) then use the lock statement.

Another reason why this exception may occur:
if (Monitor.TryEnter(_lock))
{
try
{
... await MyMethodAsync(); ...
}
finally
{
Monitor.Exit(_lock);
}
}
I get this exception on Monitor.Exit when after 'await' another thread continues execution.
Edit:
Use SemaphoreSlim, because it doesn't require releasing thread to be the same.

You will also run into this exception if you do the following:
mutex.WaitOne();
… Some Work...
await someTask;
mutex.ReleaseMutex();
That's because the code after the await can be executed on a different thread from the line just before. Basically, it seems that if you asynch code now (in early 2020), Mutexes simply don't work. Use events or something.

I have found the problem. First several things about the filterCtiCallLog class. I have designed it so to work both asynchronous and synchronous. For first I have written code for asynchronous execution. I needed a way to trigger events from child worker thread to parent, to report the working state. For this I have used AsyncOperation class and it's post method. Here is the code part for triggering CtiCallsRetrieved event.
public class FilterCtiCallLog
{
private int RequestCount = 0;
private AsyncOperation createCallsAsync = null;
private SendOrPostCallback ctiCallsRetrievedPost;
public void CreateFilteredCtiCallLogSync()
{
createCallsAsync = AsyncOperationManager.CreateOperation(null);
ctiCallsRetrievedPost = new SendOrPostCallback(CtiCallsRetrievedPost);
CreateFilteredCtiCallLog();
}
private void CreateFilteredCtiCallLog()
{
int count=0;
//do the job
//............
//...........
//Raise the event
createCallsAsync.Post(CtiCallsRetrievedPost, new CtiCallsRetrievedEventArgs(count));
//...........
//...........
}
public event EventHandler<CtiCallsRetrievedEventArgs> CtiCallsRetrieved;
private void CtiCallsRetrievedPost(object state)
{
CtiCallsRetrievedEventArgs args = state as CtiCallsRetrievedEventArgs;
if (CtiCallsRetrieved != null)
CtiCallsRetrieved(this, args);
}
}
As you can see the code is executing synchronously. The problem here is in AsyncOperation.Post() method. I presumed that if it is called in the main thread it will act as simply triggering the event, not posting it to parent thread. However it wasn't the case. I don't know how it is working, but I have changed the code, to check if the CreateFilteredCtiCallLog is called sync or async. And if it is async call I used AsyncOperation.Post method, if not, I have simply triggered the EventHandler if it is not null. Here is the corrected code
public class FilterCtiCallLog
{
private int RequestCount = 0;
private AsyncOperation createCallsAsync = null;
private SendOrPostCallback ctiCallsRetrievedPost;
public void CreateFilteredCtiCallLogSync()
{
createCallsAsync = AsyncOperationManager.CreateOperation(null);
ctiCallsRetrievedPost = new SendOrPostCallback(CtiCallsRetrievedPost);
CreateFilteredCtiCallLog(false);
}
private void CreateFilteredCtiCallLog(bool isAsync)
{
int count=0;
//do the job
//............
//...........
//Raise the event
RaiseEvent(CtiCallsRetrievedPost, new CtiCallsRetrievedEventArgs(count),isAsync);
//...........
//...........
}
public event EventHandler<CtiCallsRetrievedEventArgs> CtiCallsRetrieved;
private void RaiseEvent(SendOrPostCallback callback, object state, bool isAsync)
{
if (isAsync)
createCallsAsync.Post(callback, state);
else
callback(state);
}
private void CtiCallsRetrievedPost(object state)
{
CtiCallsRetrievedEventArgs args = state as CtiCallsRetrievedEventArgs;
if (CtiCallsRetrieved != null)
CtiCallsRetrieved(this, args);
}
}
Thanks everybody for the answers!

I have seen this happen when you lock code using a Monitor, then call an async code and you get this, when using a lock(object) you get a compiler error, however between monitor.enter(object) and Monitor.Exist(object) the compiler does not complain... unfortunately.

Using a flag to attempt to monitor a kernel synchro object state will just not work - the point of using those synchro calls is that they work correctly without any explicit checking. Setting flags will just cause intermittent problems because the flag may be changed inappropriately due to interrupts between checking the flag and acting on it.
A mutex can only be released by the threat that acquired it. If you callback is called by a different thread, (one internal to CreateFilteredCtiCallLogSync() or a kernel thread pool), the release will fail.
It's not clear exactly what you are attempting to do. Presumably, you want to serialize access to CreateFilteredCtiCallLogSync() and the callback flags that the instance is available for re-use? If so, you could use a semaphore instead - init. it to one unit, wait for it at the start and release it in the callback.
Is there some issue where sometimes the callback is not called, and hence the try/finally/release? If so this way out seems a bit dodgy if the callback is asychronous and may be called by another thread after the setup thread has left the function.

I only had this one once or twice, and in every case it came about by trying to release a mutex I didn't own.
Are you sure the events are raised on the same thread the mutex was acquired on?
Although you mention that filterCtiCallLog.CreateFilteredCtiCallLogSync() is a blocking call, perhaps it spawns of worker threads that raise the event?

Maybe not the most meaningful error message, I've seen this happen in some third party code as below,
object obj = new object();
lock (obj)
{
//do something
Monitor.Exit(obj);//obj released
}//exception happens here, when trying to release obj

I have read the thread and got some ideas. But did not know what exactly need to do to solve the issue. I face the same error when uploading the image to the s3 at nopCommerce solution.And the below code is working for me.
using var mutex = new Mutex(false, thumbFileName);
mutex.WaitOne();
try
{
if (pictureBinary != null)
{
try
{
using var image = SKBitmap.Decode(pictureBinary);
var format = GetImageFormatByMimeType(picture.MimeType);
pictureBinary = ImageResize(image, format, targetSize);
}
catch
{
}
}
if (s3Enabled)
//await S3UploadImageOnThumbsAsync(thumbFileName, pictureBinary, picture.MimeType, picture, targetSize);
// The above code was causing the issue. Because it is wait for the thread.
//So I replace the code below line and the error disappear. This also kind of same implementation by nopCommerce.
//The thread need to wait.
S3UploadImageOnThumbsAsync(thumbFileName, pictureBinary, picture.MimeType, picture, targetSize).Wait();
else
File.WriteAllBytes(thumbFilePath, pictureBinary);
}
finally
{
mutex.ReleaseMutex();
}