In the previous post C# Notify Parent From Child using events and delegates , we were just notifying the parent class about some processing happening in the child class.
But we were not sending any information or data to parent class about what processing is happening in child class. We have taken the same example taken in C# Notify Parent From Child using events and delegates and modified a bit so that we can send information to parent about the processing happening in Child class.
Previously, in Parent we were getting information that some key is pressed in Child Class. Now we will send the information that which key is pressed in Child class.
We have modified the delegate to be method with parameters. Now the signature of the event handler will also change. Also we have defined a custom class "CustomEventArgs" which has one public property i.e Key, which has the information about the pressed key.
Now whenever Child class raises an event, it will create and instance of CustomEventArgs and send it to all the event listeners. So all the event listeners, in our case the Parent class, will get the information about which key is pressed.
Source Code:
Showing posts with label Events. Show all posts
Showing posts with label Events. Show all posts
C# Notify Parent From Child using events and delegates
While creating an application, we often come across scenarios where we have parent child relationship between objects.
When we want to pass some information from parent to child, it is very simple as we have the reference of the child object in the parent and we pass the information using message passing technique, where we call some public method of child and achieve the desired result.
But many times while creating applications, we find some requirement where we need to notify the parent class that some processing has happened in child class. Based on that we need to do something in parent class. Notifying parent from child is not direct way as child do not hold reference of parent.
Note : We can always pass parent's reference to child but it is not the conventional way and can cause issues while maintaining the application. So this is not recommended.
So, we can achieve this using delegates. We can create and event in child using delegate. Parent will listen to this event. Whenever some processing happens in child, child can raise event and whoever is listening to this event will get notified that some processing has happened in child.
Sample Code:
When we want to pass some information from parent to child, it is very simple as we have the reference of the child object in the parent and we pass the information using message passing technique, where we call some public method of child and achieve the desired result.
But many times while creating applications, we find some requirement where we need to notify the parent class that some processing has happened in child class. Based on that we need to do something in parent class. Notifying parent from child is not direct way as child do not hold reference of parent.
Note : We can always pass parent's reference to child but it is not the conventional way and can cause issues while maintaining the application. So this is not recommended.
So, we can achieve this using delegates. We can create and event in child using delegate. Parent will listen to this event. Whenever some processing happens in child, child can raise event and whoever is listening to this event will get notified that some processing has happened in child.
Sample Code:
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