Creating a Custom Event

Question

Can a custom event be created for any object method  To do this do I just use the following syntax    myObject myMethod   new EventHandler myNameEvent     The following code has prompted this question      private void btRunProcessAndRefresh Click object sender EventArgs e                myProcess  new Process            myProcess StartInfo FileName     c  ConsoleApplication4 exe           myProcess Exited    new EventHandler MyProcessExited           myProcess EnableRaisingEvents  true          myProcess SynchronizingObject  this          btRunProcessAndRefresh Enabled  false          myProcess Start

User · Answer

Declare the class containing the event   class MyClass       public event EventHandler MyEvent       public void Method             OnEvent               private void OnEvent             if  MyEvent    null                MyEvent this  EventArgs Empty                       Use it like this   MyClass myObject   new MyClass    myObject MyEvent    new EventHandler myObject MyEvent   myObject Method

User · Answer

Yes  provided you have access to the object definition and can modify it to declare the custom event  public event EventHandler lt EventArgs gt  ModelChanged    And normally you d back this up with a private method used internally to invoke the event   private void OnModelChanged EventArgs e        if  ModelChanged    null          ModelChanged this  e       Your code simply declares a handler for the declared myMethod event  you can also remove the constructor   which would get invoked every time the object triggers the event   myObject myMethod    myNameEvent    Similarly  you can detach a handler using   myObject myMethod -  myNameEvent    Also  you can write your own subclass of EventArgs to provide specific data when your event fires

User · Answer

Based on  ionden s answer  the call to the delegate could be simplified using null propagation since C  6 0    Your code would simply be   class MyClass       public event EventHandler MyEvent       public void Method             MyEvent  Invoke this  EventArgs Empty             Use it like this   MyClass myObject   new MyClass    myObject MyEvent    new EventHandler myObject MyEvent   myObject Method

User · Answer

Yes you can do like this     Creating advanced C  custom events  or  The Simplest C  Events Example Imaginable  public class Metronome       public event TickHandler Tick      public EventArgs e   null      public delegate void TickHandler Metronome m  EventArgs e       public void Start                 while  true                        System Threading Thread Sleep 3000               if  Tick    null                                Tick this  e                                   public class Listener       public void Subscribe Metronome m                m Tick    new Metronome TickHandler HeardIt              private void HeardIt Metronome m  EventArgs e                System Console WriteLine  HEARD IT            class Test       static void Main                 Metronome m   new Metronome            Listener l   new Listener            l Subscribe m           m Start

User · Answer

You need to declare your event in the class from myObject    public event EventHandler lt EventArgs gt  myMethod    you should name it as an event  like ObjectChanged    then myNameEvent is the callback to handle the event  and it can be in any other class

User · Answer

Yes you can create events on objects  here is an example   public class Foo       public delegate void MyEvent object sender  object param       event MyEvent OnMyEvent       public Foo                 this OnMyEvent    new MyEvent Foo OnMyEvent              void Foo OnMyEvent object sender  object param                if  this OnMyEvent    null                          do something                        void RaiseEvent                 object param   new object            this OnMyEvent this param

[c#] Creating a Custom Event

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