How can I send validation message from DLL library

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I've Desktop application with N-Tire architecture , i want to send validation message from business layer to GUI Form to show it in MessageBox to make code more reusable and isolated.
how can i achieve this

What I have tried:

i try throw new exception , but the application crash , i just want to show message into messagebox

Posted 5-Dec-20 22:12pm

Ahmed Dabas

Updated 5-Dec-20 22:19pm

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OriginalGriff · Answer 1 · 2020-12-05T22:19:00

Solution 1

The best way is to provide an Event in the BL DLL that the PL handles - it can then deal with the message as it sees fit.

Exceptions should not be used for "normal processing" - they are there to handle exceptional events such as errors, not for confirmations. And if they aren't handled every time your DLL is called, your app will crash - that's the whole idea!

Posted 5-Dec-20 22:19pm

OriginalGriff

Comments

Ahmed Dabas 6-Dec-20 4:49am

can u support me with simple example , please

OriginalGriff 6-Dec-20 5:11am

Example of what exactly?
You don't know how to create an event?
Or you don't know how to add an event handler?

Ahmed Dabas 6-Dec-20 5:25am

i don't know how to make event fire message box

OriginalGriff 6-Dec-20 5:34am

Please read what you wrote again.

How would you make a button click event open a message box?

Ahmed Dabas 6-Dec-20 5:45am

No , i want catch the message that send by bl event and show it in messagebox

OriginalGriff 6-Dec-20 6:21am

You handle the event.
It passes you the BL class instance in the sender parameter.
You cast the sender to the BL class, and access the message via a property.
You display the message in a Message box.

What part of this have you not done before?

Ahmed Dabas 6-Dec-20 6:28am

Because i'm not using event before there is some miss understand
i'll review event concept and then try doing idea

OriginalGriff 6-Dec-20 6:54am

You've used events loads of times: every button you click, every textbox you type in, every control you drop on your forms!

Ahmed Dabas 7-Dec-20 2:19am

yes i do that , but i never write a custom event befor

OriginalGriff 7-Dec-20 2:50am

They are simple to create, and really useful:

https://www.codeproject.com/Articles/400287/A-simple-code-snippet-to-add-an-event

Ahmed Dabas 7-Dec-20 2:26am

http://www.[DELETED].com/file/[DELETED]/DemoEvent.rar/file

OriginalGriff 7-Dec-20 2:54am

You should be aware that that site is on many, many blacklists because it holds a lot of illegal / copyrighted material, and is known for virus / ransomware infected downloads.
I have removed the identifying info from your link, and you should not post such links here again.