![]() ![]() BeginInvokeīeginInvoke method take a Delegate but it executes the method asynchronously. #Dispatch definition update#It will not throws any error and successfully update the Content property. In the Invoke method, I pass the Action and update the Content property of Button object. We have used Invoke method of Dispatcher. It will throws a System.InvalidOperationException. In the InvokeMethodExample if we try to directly call to update the Content property of btn1 object. #Dispatch definition code#That means it does not return until the Dispatcher complete the execution of the method.Ībove code will create a new thread using Task.Factory and immediately start the thread. Invoke method takes an Action or Delegate and execute the method synchronously. Only Dispatcher can update the objects in the UI from non-UI thread.ĭispatcher provides two methods for registering method to execute into the message queue. When we create a new thread for offloading the work and want to update the UI from the other thread then we must need Dispatcher. WPF works with Dispatcher object behind the scenes and we don't need to work with Dispatcher when we are working on the UI thread. In the constructor, it save the reference of current thread Dispatcher to Dispatcher property of DispatcherObject. DispatcherObject contains a property of type Dispatcher. ![]() When WPF creates an instance of Button, it calls the protected constructor of DispatcherObject. How all WPF objects refers to single Dispatcher?Įvery WPF control whether it is Window, button or textbox inherits from DispatcherObject. Dispatcher execute its message queue into the synchronous order. Whenever your changes the screen or any event executes, or call a method in the code-behind all this happen in the UI thread and UI thread queue the called method into the Dispatcher queue. The UI thread queues methods call inside the Dispatcher object. WPF Dispatcher is associated with the UI thread. Render threads runs in the background and used for render the WPF screen. UI thread is responsible all the user inputs, handle events, paints screen and run the application code. When WPF application starts, it creates two threads: Run method is used for initializing the message queue. When you execute a WPF application, it automatically create a new Dispatcher object and calls its Run method. ![]() They must place their method call into the message queue to update the objects in STA.ĭispatcher owns the message queue for the STA thread. As well as other threads outside the apartment can't update the objects directly. STA have a message queue to synchronize method calls within his apartment. WPF DispatcherĪ WPF application must start in single-threaded apartment thread. ![]() All objects are self responsible for maintaining the synchronization of their data. All objects in this apartment can receive calls from any thread. Multi-threaded apartments contains one or more threads. When other threads calls an object in STA thread then the method call are queued in the message queue and STA object will receive a call from that message queue. Single-threaded apartment needs a message queue to handle calls from other threads. Objects does not need synchronization because all methods calls are comes synchronously from single thread. All objects in this apartment can receive method calls from only this thread. Single-threaded apartments contains only one thread. ![]()
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