How to use BeginInvoke C

Question

Could you explain this for me please   someformobj BeginInvoke  Action       gt        someformobj listBox1 SelectedIndex   0         Could you tell me how can I use begininvoke exactly  What is Action type  Why there is blank brackets     And what does this mean   gt

User · Accepted Answer

Action is a Type of Delegate provided by the  NET framework   The Action points to a method with no parameters and does not return a value        gt  is lambda expression syntax   Lambda expressions are not of Type Delegate   Invoke requires Delegate so Action can be used to wrap the lambda expression and provide the expected Type to Invoke    Invoke causes said Action to execute on the thread that created the Control s window handle   Changing threads is often necessary to avoid Exceptions   For example  if one tries to set the Rtf property on a RichTextBox when an Invoke is necessary  without first calling Invoke  then a Cross-thread operation not valid exception will be thrown   Check Control InvokeRequired before calling Invoke   BeginInvoke is the Asynchronous version of Invoke   Asynchronous means the thread will not block the caller as opposed to a synchronous call which is blocking

User · Answer

I guess your code relates to Windows Forms  You call BeginInvoke if you need something to be executed asynchronously in the UI thread  change control s properties in most of the cases  Roughly speaking this is accomplished be passing the delegate to some procedure which is being periodically executed   message loop processing and the stuff like that   If BeginInvoke is called for Delegate type the delegate is just invoked asynchronously   Invoke for the sync version    If you want more universal code which works perfectly for WPF and WinForms you can consider Task Parallel Library and running the Task with the according context   TaskScheduler FromCurrentSynchronizationContext     And to add a little to already said by others  Lambdas can be treated either as anonymous methods or expressions  And that is why you cannot just use var with lambdas  compiler needs a hint   UPDATE   this requires  Net v4 0 and higher     This line must be called in UI thread to get correct scheduler var scheduler   System Threading Tasks TaskScheduler FromCurrentSynchronizationContext        this can be called anywhere var task   new System Threading Tasks Task       gt  someformobj listBox1 SelectedIndex   0       also can be called anywhere  Task  will be scheduled for execution     And  IF I m not mistaken  can be  or even will be executed synchronously     if this call is made from GUI thread   to be checked   task Start scheduler     If you started the task from other thread and need to wait for its completition task Wait   will block calling thread till the end of the task   Read more about tasks here

[c#] How to use BeginInvoke C#

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