Blazor ASP.NET Core 7.0

Pages

Pages/Items.razor

@page "/items" @* url *@ @page "/item/{id:int}" @* url avec un parameter *@ <PageTitle>Items</PageTitle> @if (Items == null) @* attendre que la valeur soit chargée *@ { <p><em>Loading...</em></p> } else { /* ... */ }

Pages/Items.razor.cs

public partial class Table : ComponentBase { private IReadOnlyCollection<ItemDto> items; [Parameter] public int Id { get; set; } protected override async Task OnInitializedAsync() { items = await this.ItemClient.GetAsync(); } protected override async Task OnAfterRenderAsync(bool firstRender) { }

• Route parameters
• Route constraints
• Component lifecycle

CSS isolation

Pages/Items.razor.css

/* scoped css only for this page */ /* @import is not allowed in scoped css */

JS isolation

Pages/MyPage.razor.js

export function myFunction() { } export function myFunctionWithArg(arg) { return 'ok'; }

Pages/MyPage.razor.cs

public partial class MyPage : ComponentBase, IAsyncDisposable { [Inject] private IJSRuntime JS { get; set; } = default!; private IJSObjectReference? module; protected override async Task OnAfterRenderAsync(bool firstRender) { if (firstRender) { module = await JS.InvokeAsync<IJSObjectReference>("import", "./Pages/MyPage.razor.js"); } } private async Task MyJsFunction() { if (module is not null) await module.InvokeVoidAsync("myFunction"); } private async ValueTask<string?> MyJsFunctionWithArg(string arg) { string result = null; if (module is not null) await module.InvokeAsync<string>("myFunctionWithArg", arg); return result; } async ValueTask IAsyncDisposable.DisposeAsync() { if (module is not null) await module.DisposeAsync(); }

Form

EditItem.razor

@page "/edititem/{ItemId:int}" <EditForm Model="@item" OnValidSubmit="@HandleValidSubmitAsync" OnInvalidSubmit="@HandleInvalidSubmitAsync"> <button type="submit">Save</button> <button @onclick="Cancel">Cancel</button> </EditForm>

EditItem.razor.cs

[Parameter] public int ItemId { get; set; } [Inject] private IItemService ItemService { get; set; } private Item item = null; protected override async Task OnInitializedAsync() { item = await ItemDataService.GetItemAsync(ItemId); } // when the submit button is clicked and the model is valid private async Task HandleValidSubmitAsync() { await ItemService.UpdateItemAsync(item); } // when the submit button is clicked and the model is not valid private async Task HandleInvalidSubmitAsync() { }

Input Text

<div class="form-group row"> <label for="name" class="col-sm-3"> Item: </label> <InputText id="name" @bind-Value="Item.Name" class="form-control col-sm-8" placeholder="Enter name"> </InputText> </div>

Form validation

Data Annotation

Item.cs

[Required, StringLength(50, MinimumLength = 3, ErrorMessage = "Name must be between 3 and 50 characters")] public string Name { get; set; }

Pages/ItemEdit.razor

<EditForm Model="@item"> <DataAnnotationsValidator /> <ValidationSummary /> @* affiche la liste des messages d'erreur de validation *@ <InputText @bind-value="item.Name" placeholder="Enter name" /> <ValidationMessage class="offset-sm-3 col-sm-8" For="@(() => Item.Name)" /> @* affiche le message d'erreur de validation *@

Data binding

One way

Changes made in the UI doesn't change the binded property.
The onchange event can be used to manually update the property.

Fichier:Blazor.svg

<input type="text" value="@Description" @onchange=@((ChangeEventArgs __e) => Description = __e.Value.ToString()) @onchange=OnInputChanged /> @code { string Description { get; set; } = "Text"; void OnInputChanged(ChangeEventArgs e) => Description = e.Value.ToString(); }

Two way

Fichier:Blazor.svg

<input type="text" @bind="Description" /> @* by default uses the 'on change' event (focus lost) *@ <input type="text" @bind="Description" @bind:event="oninput" /> @* trigger the binding 'on input' event *@ @code { string Description { get; set; } = "Text"; }

Dependency injection

Program.cs

builder.Services.AddTransient<IMyService, MyService>();

Pages/MyPage.razor.cs

[Inject] private IMyService myService { get; set; }

Lifetime	Description
Singleton	creates a single instance of the service. All components requiring a Singleton service receive the same instance of the service.
Transient	creates a new instance of the service on each component request.
Scoped	creates a new instance of the service on each HTTP request but not across SignalR connection/circuit messages. Which means only when: The user closes the browser's window, then opens a new window and navigates back to the app. The user closes a tab of the app in a browser window, then opens a new tab and navigates back to the app. The user selects the browser's reload/refresh button.

Entity Framework Core

Using a DbContext factory

DbContext isn't thread safe and isn't designed for concurrent use.
To handle multi-threads scenarios, use a AddDbContextFactory to create a DbContext for each query.

Program.cs

builder.Services.AddDbContextFactory<MyDbContext>();

MyRepository.cs

private readonly IDbContextFactory<MyDbContext> contextFactory; public DataSummaryRepository(IDbContextFactory<MyDbContext> contextFactory) { this.contextFactory = contextFactory; } public async Task<Data> FetchDataAsync() { // create a DbContext for this query, then dispose it once the query has been executed using var context = contextFactory.CreateDbContext(); }

External JS libraries

LibMan library manager

# install the LibMan CLI dotnet tool install -g Microsoft.Web.LibraryManager.Cli # create a libman.js file libman init # available providers: cdnjs, jsdelivr, unpkg, filesystem # install bootstrap, only bootstrap.min.css and bootstrap.bundle.min.js (with popper) libman install bootstrap@5.0.1 \ --files dist/css/bootstrap.min.css \ --files dist/css/bootstrap.min.css.map \ --files dist/js/bootstrap.bundle.min.js \ --files dist/js/bootstrap.bundle.min.js.map # default destination path: wwwroot/lib/bootstrap libman install bootswatch@5.0.1 --files dist/darkly/bootstrap.min.css # uninstall bootstrap libman uninstall bootstrap@5.0.1

• Use LibMan with ASP.NET Core in Visual Studio

Turn on detailed errors

Program.cs

builder.Services.AddServerSideBlazor() .AddCircuitOptions(o => { o.DetailedErrors = true; o.DetailedErrors = builder.Environment.IsDevelopment(); // only add details when debugging });