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Ankit Rajput
Ankit Rajput

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How to Update One Component's State Based on Another Component's Change in Blazor Server

Hi everyone,

I'm working on a Blazor Server project and I need to update the state of one component whenever another component changes. I'm looking for the best approach to achieve this. Should I use cascading parameters, state containers, or events to trigger updates between components?

Any guidance, examples, or best practices would be greatly appreciated!

Thank you in advance!

Top comments (2)

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dr_dimaka profile image
Dmitry Pavlov

This should put some light on how fo so using just Blazor jonhilton.net/blazor-rendering/

Also if you are familiar with Flux pattern (unidirectional data flow used in many SPA frameworks/libs) I would suggest also having a look at managing state using Fluxor code-maze.com/fluxor-for-state-man...

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dee_ja_9b5bf05aa2811a59e2 profile image
dee ja

In Blazor Server, updating one component's state based on changes in another component can be achieved through shared state and event callbacks. Here's a step-by-step guide to achieve this:

  1. Use a Shared Service for State Management

Create a service to hold the shared state between components. This service will notify components when the state changes.

Example:

public class StateService
{
public event Action? StateChanged;

private string _sharedData = string.Empty;
public string SharedData
{
    get => _sharedData;
    set
    {
        _sharedData = value;
        NotifyStateChanged();
    }
}

private void NotifyStateChanged()
{
    StateChanged?.Invoke();
}
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}

  1. Register the Service in Program.cs

Register the service as a singleton in the dependency injection container.

builder.Services.AddSingleton();

  1. Inject the Service into Components

Inject the StateService into the components that need to share the state.

Component A (Updates the State):

@inject StateService StateService

Component B (Responds to State Change):

@inject StateService StateService

Updated Data: @SharedData

@code {
private string SharedData = string.Empty;

protected override void OnInitialized()
{
    StateService.StateChanged += UpdateState;
    SharedData = StateService.SharedData; // Initialize state
}

private void UpdateState()
{
    SharedData = StateService.SharedData;
    InvokeAsync(StateHasChanged);
}

public void Dispose()
{
    StateService.StateChanged -= UpdateState; // Avoid memory leaks
}
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}

  1. Use Cascading Parameters (Optional)

For simpler cases, you can use cascading values to share state between components without a service.

Example:

In a parent component:

@code {
private string SharedData = "Initial Data";
}

In ComponentA and ComponentB:

[CascadingParameter(Name = "SharedState")]
public string SharedData { get; set; }

Summary

Shared Service is the best approach for managing shared state and triggering updates across unrelated components.

Cascading Parameters are simpler but suitable for parent-child relationships.

Always manage event subscriptions to avoid memory leaks in Blazor Server applications.

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