Exploring EventCallback in Blazor: Building Interactive Components

Introduction:

Blazor is a powerful framework for building web applications using C# instead of JavaScript. It allows developers to create interactive and dynamic user interfaces with ease. One of the key features in Blazor is the EventCallback<T> pattern, which enables communication between components through events. In this blog post, we will explore how to use the EventCallback<T> pattern in Blazor by building a simple example.

Creating the Event-Driven Component:

Let's start by creating a Blazor component called MyComponent. This component will raise an event when a button is clicked. Here's the code for the MyComponent.razor file:

MyComponent.razor

<h3>My Component</h3>

<button @onclick="RaiseEvent">Raise Event</button>

@code {
    [Parameter]
    public EventCallback<string> EventRaised { get; set; }

    private async Task RaiseEvent()
    {
        await EventRaised.InvokeAsync("Event Data");
    }
}

In this code, we define the EventRaised parameter as an EventCallback<string>, which represents the event that can be registered to from the parent component. When the button is clicked, the RaiseEvent method is invoked, and the event is raised by calling InvokeAsync and passing in the event data.

Add handler to the Event in the Parent Component:

Now let's create a parent component called ParentComponent that will consume the MyComponent and handle the raised event. Here's the code for the ParentComponent.razor file:

ParentComponent.razor

@page "/parent"

<h3>Parent Component</h3>
<MyComponent EventRaised="HandleEvent" />

<p>Event Data: @eventData</p>

@code {
    private string eventData;

    private void HandleEvent(string data)
    {
        eventData = data;
    }
}

In this code, we use the MyComponent component and attach to its EventRaised event by specifying the HandleEvent method as the event handler. The HandleEvent method will be called when the event is raised in MyComponent, and it simply assigns the event data to the eventData property.

In the above GIF, the image illustrates the functioning of the EventCallback<T> in Blazor. The parent component is distinguished by a gray background, while the child component is highlighted with a blue background. When the user clicks on the button within the child component, the value is displayed in the parent component.

Conclusion:

In this blog post, we explored the EventCallback<T> pattern in Blazor, which allows components to communicate with each other through events. We built a simple example with a child component (MyComponent) that raises an event and a parent component (ParentComponent) that responds to and handles the event. This pattern enables the creation of interactive and dynamic Blazor applications, providing a seamless experience for users.

I hope you found it informative and helpful. If you have any questions or feedback, feel free to leave a comment below. Happy coding!