Blazor component lifecycle events

Lifecycle of Blazor Components

Blazor components have a lifecycle that defines the various stages a component goes through from its creation to its disposal. Understanding the component lifecycle is crucial for managing state, optimizing performance, and responding to events. Here's an overview of the Blazor component lifecycle events along with sample code to illustrate each stage:

• Initialization: This is the initial stage where the component's parameters and dependencies are set. It happens before rendering.

@code {
    [Parameter] public string Message { get; set; }

    protected override void OnInitialized()
    {
        // Initialization logic
    }
}

<h3>@Message</h3>

• Initialize a database connection
• Load data from a server
• Set up bindings
• Create timers or other asynchronous tasks

• Parameter Set: This stage occurs when component parameters are set. It can be useful for reacting to changes in parameters.

@code {
    [Parameter] public string Message { get; set; }

    protected override void OnParametersSet()
    {
        // Parameter set logic
    }
}

<h3>@Message</h3>

• Update the component's title
• Update the data it is displaying
• Change its behavior based on the new parameters

• Render: This is where the component's rendering logic occurs. It happens after parameters are set.

@code {
    [Parameter] public string Message { get; set; }

    protected override void BuildRenderTree(RenderTreeBuilder builder)
    {
        // Render logic
    }
}

<h3>@Message</h3>

• OnAfterRender/OnAfterRenderAsync: These events occur after the component has been rendered and added to the UI. They are useful for interacting with the rendered DOM elements.

@code {
    [Parameter] public string Message { get; set; }

    protected override void OnAfterRender(bool firstRender)
    {
        if (firstRender)
        {
            // Logic to execute after first render
        }
    }
}

<h3>@Message</h3>

• Update the component's state in response to user input
• Make asynchronous calls
• Handle errors

• Update: This stage happens when the component needs to update due to changes in parameters or state.

@code {
    private int count = 0;

    private void IncrementCount()
    {
        count++;
    }

    protected override bool ShouldRender()
    {
        // Custom logic to determine whether to render
        return true;
    }
}

<button @onclick="IncrementCount">Increment</button>
<p>Count: @count</p>

• Dispose: This is the final stage when the component is removed from the UI. It's useful for cleaning up resources.

@implements IDisposable

@code {
    // Component logic

    public void Dispose()
    {
        // Cleanup logic
    }
}

Remember that Blazor also has asynchronous versions of some lifecycle events, such as OnInitializedAsync, OnParametersSetAsync, and OnAfterRenderAsync. These can be used when you need to perform asynchronous operations during those stages.

It's important to note that you might not always need to use all of these lifecycle events for every component. Choose the ones that fit your needs and make your code efficient and maintainable.