Every program created for computers or mobile devices has to react to specific events. Otherwise, nothing would happen when an individual taps on a button on the screen of a smartphone. Even the smallest and most insignificant applications print outputs in response to events. Now, if you continue adding features to a program, then you increase the number of events to which the program has to respond. The commands would come in the form of a button click or an incoming message. It means that the strategy that you use to handle events will have a massive impact on the overall maintainability of the codebase.

According to an expert on asp dot net development, Prism is an extensive library for app development purposes in .NET. It has several incredible features that can ease the lives of every C# developer. If you develop mobile apps using .NET, then this topic is for you. Among all the features included in the Prism library, there is one called the EventAggregator. Here you’ll learn a few things about EventAggregator, including why it’s useful and where you should use it. You’ll also learn a bit about how to use Prism EventAggregator.

About Prism EventAggregator

So, what is EventAggregator? An asp dot net development expert explains that it’s Prism’s implementation of the Publisher-Subscriber pattern. Publisher-Subscriber happens to be a messaging pattern designed for asynchronous communication in an application. To be specific, it solves all common issues concerning sending messages between components. Some of these components are often difficult, impractical, or impossible to link.

Prism EventAggregator pattern consists of events published to an event bus, which in turn passes them to one or more subscribers. These subscribers can hand the event the way they want to.

Reasons to use

Many renowned and reputable providers of dot net development services use EventAggregator. Why do they do it? Here are the reasons.

    • It’s decoupled: EventAggregator has a decoupled nature where Publishers and Subscribers don’t know anything about each other.


    • It’s asynchronous: As it’s asynchronous, the Publisher can send a message quickly and continue its own work without waiting for the Subscriber to finish handling the event.


    • Separation of concerns: The Publisher doesn’t need to know what the Subscriber does with the event. Similarly, the Subscriber doesn’t need to know about the origin of the event.


  • It’s scalable: Regardless of the number of Publishers, Subscribers, and events you have, you would only have to refer to one event bus.

Apart from these benefits, EventAggregator has a few more that are particularly useful in providing dot net development services for mobile applications.

features of Prism EventAggregator


    • Preventing memory leaks: EventAggregator will never keep any reference of a discarded Subscriber. Understandably, there’s no need to unsubscribe anything manually.


    • Sending complex objects: With EventAggregator, it gets easier to send complex objects as a parameter when publishing an event to give the Subscriber more context and info while handling the event.


    • Thread flexibility: You get to choose the thread that you want to use to handle incoming events.


  • Filtering events: Finally, Subscribers can choose the events that they want to process and ignore the others.

When to use

Now, a .NET development specialist from an MVC development company already explained that the Publisher-Subscriber pattern helps in establishing communication between components that are difficult or impractical to link. In a Prism project, the best developers often use EventAggregator to send messages between two or more ViewModels, or between services that don’t have any reference to each other. Another use case worth mentioning is when different Subscribers must handle one event. During such situations, it won’t be practical to pass a Publisher reference to all these Subscribers.

In Xamarin.Forms

If you have knowledge in Xamarin.Forms, then you’re probably thinking that it has something like EventAggregator already. The experts of the best MVC development company concur. They know that Xamarin.Forms has its own implementation of Publisher-Subscriber called MessagingCenter. Regardless of this fact, they choose EventAggregator for the following reasons.

    • Memory leaks: MessagingCenter will keep a reference of any Subscriber that you remove. You have to unsubscribe manually to get rid of it permanently.


    • Flexibility: Unlike EventAggregator, MessagingCenter doesn’t have thread flexibility or event filters.


  • Testing ability: MessagingCenter always uses static methods that make writing unit tests much more challenging. Prism, on the other hand, automatically injects an EventAggregator into the constructor. As a result, you can mimic it easily.

A few things to remember

By now, the flexibility and utility powers of EventAggregator should be clear to you. However, as always, there’s a catch. You must keep an eye out for a few things.

While EventAggregator holds weak references to Subscribers online, it’s always possible that it will hold a strong reference if the Publisher passes a parameter and the Subscriber holds a reference to the same. Therefore, you should consider unsubscribing manually whenever you dispose of a Subscriber.

Also, there’s a problem with the decoupled structure of EventAggregator. It can complicate things if you overuse it. There could be a separation of concerns between the Subscriber and Publisher, but there shouldn’t be anything of that sort between the events themselves. The situation could obscure communication flow when you handle multiple events.

To conclude

The best thing to do would be to use EventAggregator as and when necessary. Avoid structuring entire projects around it. Just like everything else, maintaining moderation is the solution. Every program has to react to specific events. When X happens, so does Y. Even the most trivial application prints output in response to events. Understandably, if you add too many features to a problem, then they have to respond to button clicks or incoming messages more than usual. An asp dot net development specialist will describe why using Prism EventAggregator would be beneficial in such situations.

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Jayanti Katariya

Jayanti Katariya is the CEO of Moon Technolabs, a fast-growing IT solutions provider, with 18+ years of experience in the industry. Passionate about developing creative apps from a young age, he pursued an engineering degree to further this interest. Under his leadership, Moon Technolabs has helped numerous brands establish their online presence and he has also launched an invoicing software that assists businesses to streamline their financial operations.

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