Blazor.Core 1.1.4

Blazor Core

Install from Nuget.

dotnet add package Blazor.Core --version <latest-version>

Components

This library provides a base component class to easily inject scope services. Simply have your component inherit BaseScopeComponent class and mark your property with InjectScopeAttribute attribute. Then during BaseScopeComponent.OnInitialized the scoped serivces will automatically be injected to these fiel(s).

@inherits BaseScopeComponent

@code
{
  // This will be done automatically
  [InjectScope]
  private MyScopeService ScopeService { get; set; } = null!;

  // If you do override OnInitialized() always make sure
  // to call the base.Onitialized()
  // protected override void OnInitialized()
  // {
  //   base.Onitialized();
  // }
}

Another attribute provided in this library is AutoImportJsModule. This attribute is used to automatically import scope module class derived from BaseJsModule. It provides a convinient way to call BaseJsModule.ImportAsync() implicitly, but it must be used with InjectScope attribute.

@inherits BaseScopeComponent

@code
{
  // Inject and import automatically
  [InjectScope, AutoImportJsModule]
  private MyScopeModule ScopeModule { get; set; } = null!;

  // If AutoImportJsModule is not provided,
  // you would have to do it explicitly like below
  // protected override async Task OnAfterRenderAsync()
  // {
  //   await base.OnAfterRenderAsync();
  //   await _myScopeModule.ImportAsync();
  // }
}

Interop

This library provides a base class, BaseJsModule, that consumers can use to implement their own JS modules.

Callback Interop

More importantly this library provides a TypeScript module that serializes/deserialize C# callbacks (Func, Action, etc.) to JS. This allows C# code to pass let's say a Func<> to JS, and JS code can invoke the C# callback. To use this functionality you must have a reference to a DotNetCallbackJsModule object and then call its ImportAsync() to import the dotnet-callback.js module. Then call RegisterAttachReviverAsync().

Your code in Program.cs may look like this.

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Services
  .AddSingleton<DotNetCallbackJsModule>()
  .AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

var webHost = builder.Build();

// Only need to import and register once and can be disposed right away
var dotnetCallbackModule = webHost.Services.GetRequiredService<DotNetCallbackJsModule>();
await dotnetCallbackModule.ImportAsync();
await dotnetCallbackModule.RegisterAttachReviverAsync();
await dotnetCallbackModule.DisposeAsync();

await webHost.RunAsync();

Alternatively you can just call the extension method RegisterAttachReviverAsync to do what's described above.

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Services
  .AddSingleton<DotNetCallbackJsModule>()
  .AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

var webHost = builder.Build();

await webHost.Services.RegisterAttachReviverAsync();
await webHost.RunAsync();

Then you can use it like this.

// Action
Action action = () => Console.WriteLine("Hello World!");
ActionCallbackInterop actionCallbackInterop = new(action);

// Func
Func<int, Task<int>> func = (number) => Task.FromResult(0);
FuncCallbackInterop<int, Task<int>> funcCallbackInterop = new(func);

// Then pass the callback interop objects to a IJSRuntime's or
// IJSObjectReference's Invoke<Void>Async method. The callback
// interop objects will be correctly serialized to JS callback
IJSRuntime jsRuntime = ...
await jsRuntime.InvokeVoidAsync("myFunction", action, func);

// Make sure to clean up the callback interop objects when
// they're no longer in use. Note that if you dispose them
// before JS code calls them, an exception will be thrown.
// So make sure to only dispose once you're sure JS code
// has called them.
actionCallbackInterop.Dispose();
funcCallbackInterop.Dispose();

Define Custom Module Example

Your custom module may look like this.

In your math.ts:

export function add(a: number, b: number): number {
  return a + b;
}

Define your module like this, MathJsModule.cs:

public sealed class MathJsModule : BaseJsModule
{
  /// <inheritdoc/>
  protected override string ModulePath { get; }

  public MathJsModule(IJSRuntime jSRuntime) : base(jSRuntime)
  {
    var customPath = "js/math.js";
    ModulePath = $"{ModulePrefixPath}/{customPath}";
  }

  public async Task<int> AddAsync(int a, int b)
    => await Module.InvokeAsync<int>("add", a, b);
}

Then in your application code (most likely in Blazor), add the module class to your DI container, and use the module like this:

@implements IAsyncDisposable
@inject MathJsModule MathModule

<p>Sum is @_sum</p>

@code
{
  private int _sum;

  protected override async Task OnInitializedAsync()
  {
    await base.OnInitializedAsync();

    // You must first load the module otherwise
    // using it will cause exception
    await MathModule.ImportAsync();

    _sum = await MathModule.AddAsync(3, 2);
  }

  // Make sure to dispose the module object
  public async ValueTask DisposeAsync()
  {
    await MathModule.DisposeAsync();
  }
}

String Enum

This library also includes a class named StringEnum. Purpose of this class is to represent discrete values as string, like enum but uses string.

To define your custom string enum, inherit StringEnum like the example below.

public sealed class Color : StringEnum
{
  // Make this private so that no one else can create Color object
  private Color(string value) : base(value) {}

  public readonly static Color Blue = new("blue");

  public readonly static Color Green = new("green");

  public readonly static Color Red = new("red");
}

// Usage
Color blue = Color.Blue;
string blueStr = blue; // Implicit cast to string - blueStr is now "blue"

Defining multiple enums with the same value is not allowed. Doing so will cause an exception during runtime.

public sealed class Color : StringEnum
{
  private Color(string value) : base(value) {}

  public readonly static Color Blue = new("blue");

  public readonly static Color Green = new("blue"); // ❌ Cannot have two "blue" in a string enum
}

Converters

To make it easy to work with JSOn serialization, this library includes this converter StringEnumConverter<T>. This converter enables serializing a StringEnum to a literal string value.

Note this is a converter for System.Text.Json.

using System.Text.Json.Serialization;

[JsonConverter(typeof(StringEnumConverter<Color>))]
public sealed class Color : StringEnum
{
  private Color(string value) : base(value) {}

  public readonly static Color Blue = new("blue");

  public readonly static Color Green = new("green");

  public readonly static Color Red = new("red");
}

var json = JsonSerializer.Serialize(Color.Red);
// With the converter, json is "\"red\""
// Without the converter, json is "{\"Value\":\"red\"}"