what is the need of custom event

Question

1.00/5 (1 vote)

See more:

I have seen so many articles on creating and handling custom events in c#.But in every case I'm seeing they are calling a delegate and the main thing which is to be executed is written in a function.That function is called by the event.

But my question is why should I use an event?I can call the function directly where needed.

So can you provide an article where I can see the actual and practical purpose of creating event.I need discussion in this way-------

1)this is the work of event and
2)this thing can not be achieved by calling function or if we call a function this is the constraints.

Posted 23-Jun-15 19:32pm

souvikcode

Add a Solution

Comments

Stefan_Lang 24-Jun-15 1:51am

I am not familar with C# and can therefore not offer language-specific advice.

However, events are a language-independend concept: they are most often used to synchronize threads, by notifying them of a change that may be relevant to them. E. g. in Windows, the window drawing routines are within a separate that gets notification events every time something happens that may require a redraw, e. g. a mouse move, mouse click, border drag, a window maximize/minimize/restore command, activating a window, etc..

Users can define events for similar purposes, e. g. if you have a window showing financial data, and another thread streaming current data, the latter can send events every time one of the items that you have flagged for tracking changes. This way you can program a ticker with real time financial data.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Ralf Meier · Answer 1 · 2015-06-23T20:36:00

Solution 2

You use an Event for example when you want to create a Notification to a someone you don't know while developing the function.

Perhaps see a Button. This Control creates/fires several Events which COULD be used but NOT MUST be used. The Developer of the Button didn't know if someone will use something of this - but he gave the possibility ...

Posted 23-Jun-15 20:36pm

Ralf Meier

Comments

souvikcode 24-Jun-15 6:21am

But actually I can call button events dynamically.I want to know why custom event needed.Where required I can call the function directly.
Can you give an example where event is must used?

souvikcode 24-Jun-15 6:25am

Your button example is fine.I got it.But I can not raise button click event my self by a function.I can write a function when user click a button.Microsoft has created each and every possible user interaction event for a button.So why I need more?Your point is right.A developer can use event in his way.But he can also use my created function in his way.

Ralf Meier 24-Jun-15 7:00am

I think, my example is not so bad.
The Problem in the Moment is, that I don't imagine what you want to do.
But we could stay by this example.
It makes no difference, which kind of class you create. Perhaps you create a Button. This Button should work for all users. Now ... which functions would you build in ? Perhaps you only need the Click-Event. But another user could need the Down-Event. Now you do the following : you implement all Events (Actions which come out of your class and for which you don't want to ask), you could imagine that they could be necessary and let the user decide which and how to use them.

Perhaps this is better ...

souvikcode 29-Jun-15 0:52am

What I have understood is-------------------------

Let I've created a custom event,say grid update event.Now when any cell of a datagridview is changed my event is fired.Right?

Now I have a function which will be executed in this event.

Now for every cell update, my update function will be called automatically,I don't have to call the update function manually.Or,for another developer,he need not to know about the update function.

But,if I call the function manually all time by not creating event,that will also create the perfect development and perfect result,but that's not a good practice and time consuming.

Am I in right way?

Ralf Meier 6-Jul-15 2:25am

Sorry for the late response to your reply ...
I think, you are in the right way.
Now, what is interestinh in Events is :
Depending on your development, the user gets Information about the Sender of the Event.
Depending on your Eventargs-Class (perhaps you build a customized one) the user gets Information about the actual state of the control when calling the Event - that might be a difference to later calls of an internal method.

souvikcode 7-Jul-15 11:41am

Thanks Ralf.I'll try to make a small project implementing event and that is the best thing to learn any thing.

OriginalGriff · Answer 2 · 2015-06-23T19:41:00

Solution 1

Have a look at this: Transferring information between two forms, Part 2: Child to Parent[^] - it uses an event to pass data between two forms without breaching OOPs rules.

Posted 23-Jun-15 19:41pm

OriginalGriff