C# Academy · Lesson

State Management in Blazor

Manage shared state with service singletons, Fluxor, or cascading AppState to keep UI consistent across components.

Lesson 4 of 412 steps

State Management in Blazor is a free C# Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, and your progress syncs across the web and the CoddyKit app. The C# Academy course includes 4 lessons in total.

State Management Challenges in Blazor

As Blazor apps grow, managing state that must be shared across many unrelated components becomes complex. Simple prop-drilling breaks down; you need a centralized, reactive state store.

Simple State with a Scoped Service

The simplest Blazor state management: a scoped service that holds state and exposes an event so components can subscribe to changes.

public class CartState
{
    private readonly List<CartItem> _items = new();
    public IReadOnlyList<CartItem> Items => _items;
    public int Count => _items.Sum(i => i.Quantity);

    public event Action? OnChanged;

    public void Add(Product p)
    {
        var existing = _items.FirstOrDefault(i => i.ProductId == p.Id);
        if (existing is not null) existing.Quantity++;
        else _items.Add(new CartItem { ProductId = p.Id, Name = p.Name, Price = p.Price });
        OnChanged?.Invoke();
    }
}

Subscribing to State Changes

Components subscribe to the state service's OnChanged event and call StateHasChanged to re-render. Remember to unsubscribe in Dispose.

@inject CartState Cart
@implements IDisposable

<p>Cart: @Cart.Count items</p>

@code {
    protected override void OnInitialized()
    {
        Cart.OnChanged += OnCartChanged;
    }

    private void OnCartChanged()
    {
        InvokeAsync(StateHasChanged);
    }

    public void Dispose() =>
        Cart.OnChanged -= OnCartChanged;
}

CascadingValue as a State Container

Wrap your root layout in a CascadingValue with your state service. All descendants can access it without explicit prop threading.

@* MainLayout.razor *@
@inject CartState Cart

<CascadingValue Value="Cart">
    @Body
</CascadingValue>

@* Any nested component: *@
@code {
    [CascadingParameter]
    public CartState Cart { get; set; } = default!;

    private void Buy(Product p) => Cart.Add(p);
}

Fluxor: Flux Pattern for Blazor

Fluxor brings Redux-style unidirectional data flow to Blazor: State → Component → Action → Reducer → State. Great for complex applications.

// dotnet add package Fluxor.Blazor.Web

// State record
[FeatureState]
public record CounterState(int Count = 0);

// Actions
public record IncrementAction(int Amount = 1);

// Reducers
public static class CounterReducers
{
    [ReducerMethod]
    public static CounterState Reduce(CounterState state, IncrementAction action)
        => state with { Count = state.Count + action.Amount };
}

// Registration:
builder.Services.AddFluxor(opt =>
    opt.ScanAssemblies(typeof(Program).Assembly));

Using Fluxor in a Component

Inject IState<T> to read state and IDispatcher to dispatch actions. InheritsFrom<FluxorComponent> (or the mixin) auto-subscribes to state changes.

@inherits FluxorComponent
@inject IState<CounterState> CounterState
@inject IDispatcher Dispatcher

<p>Count: @CounterState.Value.Count</p>
<button @onclick="Increment">+1</button>
<button @onclick="() => Dispatcher.Dispatch(new IncrementAction(5))">+5</button>

@code {
    private void Increment()
        => Dispatcher.Dispatch(new IncrementAction(1));
}

LocalStorage Persistence

Persist state across page refreshes using browser localStorage via JavaScript interop. Restore it on app startup.

@inject IJSRuntime JS

@code {
    private async Task SaveStateAsync()
    {
        var json = JsonSerializer.Serialize(_state);
        await JS.InvokeVoidAsync("localStorage.setItem", "appState", json);
    }

    protected override async Task OnInitializedAsync()
    {
        var json = await JS.InvokeAsync<string?>("localStorage.getItem", "appState");
        if (json is not null)
            _state = JsonSerializer.Deserialize<AppState>(json) ?? new();
    }

    private AppState _state = new();
}

Blazored.LocalStorage Package

The Blazored.LocalStorage package provides a clean, typed API over browser localStorage without hand-writing JS interop calls.

// dotnet add package Blazored.LocalStorage
builder.Services.AddBlazoredLocalStorage();

@inject ILocalStorageService LocalStorage

@code {
    protected override async Task OnInitializedAsync()
    {
        _cart = await LocalStorage.GetItemAsync<List<CartItem>>("cart") ?? new();
    }

    private async Task SaveCartAsync()
    {
        await LocalStorage.SetItemAsync("cart", _cart);
    }

    private List<CartItem> _cart = new();
}

URL State with NavigationManager

Use query parameters to hold state that should survive a page refresh and be bookmarkable. Read and write them via NavigationManager and the URI builder.

@inject NavigationManager Nav
@page "/products"

@code {
    [SupplyParameterFromQuery] public string? Search { get; set; }
    [SupplyParameterFromQuery] public int Page { get; set; } = 1;

    private void UpdateSearch(string s)
    {
        Nav.NavigateTo(
            Nav.GetUriWithQueryParameters(
                new Dictionary<string, object?>
                {
                    [nameof(Search)] = s,
                    [nameof(Page)]   = 1
                }));
    }
}

Real-World: Shopping Cart State

A complete pattern: scoped CartState service with events, persisted to localStorage on change, and restored on load.

public class CartState
{
    private readonly ILocalStorageService _storage;
    private List<CartItem> _items = new();
    public event Action? OnChanged;

    public CartState(ILocalStorageService storage) => _storage = storage;

    public async Task InitAsync()
    {
        _items = await _storage.GetItemAsync<List<CartItem>>("cart") ?? new();
    }

    public async Task AddAsync(Product p)
    {
        var item = _items.FirstOrDefault(i => i.ProductId == p.Id);
        if (item is not null) item.Quantity++;
        else _items.Add(new CartItem { ProductId = p.Id, Name = p.Name });
        await _storage.SetItemAsync("cart", _items);
        OnChanged?.Invoke();
    }
}

Quick Check

Which state management approach is best for a simple Blazor app with limited shared state?

Answer it in the interactive lesson

Recap: State Management in Blazor

Key takeaways:

Scoped service + Action event: simplest shared state, good for most apps
CascadingValue wrapping the root provides app-wide access without prop-drilling
Fluxor: Redux-style unidirectional flow for complex state logic
Persist state to localStorage with IJSRuntime or Blazored.LocalStorage
URL state (SupplyParameterFromQuery) for bookmarkable, shareable UI state
Always unsubscribe from events in Dispose to prevent memory leaks

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Frequently Asked Questions

Is the “State Management in Blazor” lesson free?

Yes — the full text of “State Management in Blazor” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO. The C# Academy course includes 4 lessons in total.

What will I learn in “State Management in Blazor”?

Manage shared state with service singletons, Fluxor, or cascading AppState to keep UI consistent across components. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C# Academy?

No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.

How long does the “State Management in Blazor” lesson take?

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