NSNotificationCenter / BroadcastReceiver In C# .NET

Hussein Juybari

C#.NETBroadcastReceiver In C#NSNotificationCenter In C#

13 Comments

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Alaa Masalmeh8y ago
Would you please apply Singleton pattern on NotificationCenter class and abstract it to interface for IoC?
- Hussein Juybari8y ago
  Not now, because it would have breaking change for the developers using it. It will change with major version
Tridip Bhattacharjee8y ago
Now i guess this library will broadcast in my application because i though it can communicate over the internet. anyways thanks for answering.
- Hussein Juybari8y ago
  It uses in your application, You can't communicate over the internet.
Tridip Bhattacharjee8y ago
Suppose i have developed a windows application where i will use NotificationCenter lib where i will use key like demo. the same windows application one will run in india pc and another one run in london pc. so when app run in india pc will broadcast something then how the apps which is running in london pc will be notofied? there is no server so how one can send notification to other ? please share the info. thanks for your all reply.
- Hussein Juybari8y ago
  This library broadcast something in your code with an identifier which means which action will be invoked their key was notified with or without an object.
- Hussein Juybari8y ago
  You have the SetBadge key which means just setting badge to a control and another key the MessageReceive which show a message to a list. When you notify SetBadge key it will invoke just action for SetBadge you've before subscribed it.
Tridip Bhattacharjee8y ago
I guess i can use this library to notify others when my data changes. if possible when i will send notification then i guess i will get the same notification....so how to know which client sending this notification ?
- Hussein Juybari8y ago
  You should notify with an object, Your object should have value for checking who sent it
Tridip Bhattacharjee8y ago
You did not mention how to acquire the key.....from where to acquire the key?
- Hussein Juybari8y ago
  You determine what is key. Key is an identifier. It could be anything. Think set a unique name for an action.
Tridip Bhattacharjee8y ago
Can i used this library when working with dotnet v4.0 or v4.5 ?
- Hussein Juybari8y ago
  Yes, you can use it in v4.0 or v4.5

If you are an iOS or Android developer, you must have some experience in using NSNotificationCenter or BroadcastReceiver. But if you don't know what I'm talking about, don’t worry, I will explain what exactly these classes do and why and when we should use them.

What is NSNotificationCenter or BroadcastReceiver?

Apple said,

A notification dispatch mechanism that enables the broadcast of information to registered observers.

Google says,

Android apps can send or receive broadcast messages from the Android system and other Android apps, similar to the publish-subscribe design pattern. These broadcasts are sent when an event of interest occurs. For example, the Android system sends broadcasts when various system events occur, such as when the system boots up or the device starts charging. Apps can also send custom broadcasts, for example, to notify other apps of something that they might be interested in (for example, some new data has been downloaded).

How can I use these in C#?

It’s super easy. As Google said, this feature uses publish-subscribe design pattern. It means you subscribe an action with key and perform/notify this key for all subscribers who have subscribed on this key which means you can perform/notify some actions with key and pass some objects to do a specific action.

Could you explain with an example?

Yes!

Think about an app you have which supports messaging or PushNotification. So, when a message is received, you should perform some actions for showing the message received or store/read some data from the database. You should show the message in the inbox, set badge number in Tabbar or Toolbar, store that message to the database, and reload your View etc.

So, you should use events or define some static classes and static events to handle all of these actions.

Take to the code

First, install NotificationCenter package from NuGet Package Manager or run this command in NuGet Package Manager console.

PM> Install-Package NotificationCenter

This library is PCL class and you can use it in .NET Core, Xamarin, and UWP projects.

Subscribe to an action

With this code, you can subscribe to an action with key.

//In inbox page controller
NotificationCenter.Subscribe("MessageReceivedKey",SetBadge);
private void SetBadge()
{
Debug.WriteLine("Great message received so increase inbox badge");
}

//In database class
NotificationCenter.Subscribe("MessageReceivedKey",StoreOnDatabase);
private void StoreOnDatabase(object message)
{
Debug.WriteLine("Great message received so i should insert 'message' argument to database");
}

Notify/Perform an Action

So now, when a message is received, it’s time to notify the subscribers of their actions like this code.

// In message receiver event method
NotificationCenter.Notify(key: "MessageReceivedKey",data: MessageObject);

Unsubscribe on key

If you have some unused key, it’s better to unsubscribe from it like this,

NotificationCenter.Unsubscribe(key: "MessageReceivedKey");

NotificationCenter.UnsubscribeAll();

Thanks for reading my article. I hope this library helps you to make a great app.

This library is opensource and is available on GitHub website.