Threads c sharp

Threads c sharp

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  C# Threads GUIDEDBY, G.SURESH.,DEPT.OF MCA PRESENTED BY, S.KARTHICK[MCA969] P.MUTHU KUMAR[MCA976] P.MURUGESAN[MCA977] A.SENTHIL KUMAR[MCA999]
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  Thread Class EveryWin32 thread is passed a function to run when created. When the thread returns from the function it terminates. In C#, Threads are managed by the System.Threading.Thread class. C# threads are passed a static or instance function of some C# class using a standard delegate of type ThreadStart .
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  Starting C# ThreadsThread thread = new Thread(new ThreadStart(ThreadFunc)); thread.Start(); ThreadFunc can be: Static or instance member of the class instance that created the thread Static or instance member of some other class, e.g.: ThreadStart(SomeClass.aStaticFunction); ThreadStart(someClassInstance.aNonStaticFunction);
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  Thread States Athread that has been started, but not yet terminated can be in one of the following states: Running Waiting to run Suspended Blocked
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  Thread Properties IsBackground – get, set Process does not end until all Foreground threads have ended. Background threads are terminated when application ends. CurrentThread – get, static Returns thread reference to calling thread IsAlive – get Has thread started but not terminated? Priority – get, set Highest, AboveNormal, Normal, BelowNormal, Lowest ThreadState – get Unstarted, Running, Suspended, Stopped, WaitSleepJoin, ..
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  Sharing Resources Achild thread often needs to communciate with its parent thread. It does this via some shared resource, like a queue.
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  Synchronization When twoor more threads share a common resource access needs to be serialized - a process called synchronization. Consider the shared queue on the previous slide. Should the parent start to enqueue an element in an empty queue, but have its time-slice expire before finishing, the queues links are in an undefined state. Now, if the child thread wakes up, and attempts to dequeue an element the result is undefined.
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  Synchronization with C#Lock // send messages to child thread string msg = &quot;&quot;; for(int i=0; i<50; ++i) { msg = &quot;message #&quot; + i.ToString(); Console.Write(&quot;\n Sending {0},&quot;,msg); // Enqueuing changes links so must lock lock(demo.threadQ) { demo.threadQ.Enqueue(msg); } // control writer speed - twice as fast as reader Thread.Sleep(50); } lock(demo.threadQ) { demo.threadQ.Enqueue(&quot;end&quot;); } child.Join(); Console.Write( &quot;\n\n child thread state = {0}\n\n&quot;,child.ThreadState.ToString() );
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  Demonstration Program QueuedMessagesfolder Illustrates communication between parent and child threads using a queue. Also illustrates use of C# lock operation.
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  Other Locking MechanismsThe .Net Threading Library also provides: Monitor Locks an object, like C# lock, but provides more control. Interlocked Provides atomic operations on 32 bit and 64 bit data types, e.g., ints, longs, pointers. Mutex Guards a region of code. Can synchronize across process boundaries. AutoResetEvent and WaitOne Allows fine-grained control of the sequencing of thread operations. ReaderWriterLock Locks only when writing, allowing free reads.
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  Locking Certain CollectionsArrayList, Hashtable, Queue, Stack, and other collections provide Synchronized() function, supporting high performance locking. ArrayList unsync = new ArrayList(); ArrayList sync = ArrayList.Synchronized(unsynch); Your code needs no lock constructs with sync.
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  Method Decoration Methodscan be decorated with a MethodImpl attribute, synchronizing access much like a Win32 critical section. [MethodImpl (MethodImplOptions.Synchronized)] string myMethod(string input) { … } Note that this synchronizes a region of code, while lock and Monitor synchronize objects.
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  WinForms and WorkerThreads A UI thread is a thread that creates a window. A worker thread is a thread spawned by a UI thread to do work in the background while the UI thread services UI messages. A worker thread must never access UI functions directly. It accesses them through Form’s Invoke, BeginInvoke, and EndInvoke functions, passing a delegate as an argument.
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  BeginInvoke Example for(i = 1; i <= 25; i++) { s = &quot;Step number &quot; + i.ToString() + &quot; executed&quot;; Thread.Sleep(400); // Make asynchronous call to main form. // MainForm.AddString function runs in main thread // because we activated the delegate through form's // Invoke (synchronous) or BeginInvoke (asynchronous) functions. // To make synchronous call use Invoke. m_form.BeginInvoke(m_form.m_DelegateAddString, new Object[] {s}); // check if thread is cancelled if ( m_EventStop.WaitOne(0, true) ) { // clean-up operations may be placed here // ... // inform main thread that this thread stopped m_EventStopped.Set(); return; } } Delegate arguments passed as an array of objects
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  Demonstration Programs ProcessDemoand ProcessDemoWin32 Illustrates creating a child process QueuedMessages Illustrates communication between threads using queues and the C# lock operation. FormInvokeDemo folder A more interesting demonstration of the above. WorkerThread folder Simple Demonstration of UI and Worker thread communication using Form.Invoke(…) ThreadPoolDemo folder Illustrates how to use the ThreadPool to run functions
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  End of Presentation