Blazor WebAssembly WebWorkers and SharedWebWorkers
SpawnDev.BlazorJS
An easy Javascript interop library designed specifically for client side Blazor.
Supports Blazor WebAssembly .Net 6, 7, and 8.
Use Javascript libraries in Blazor without writing any Javascript code.
Alternative access to IJSRuntime JS is globally available without injection and is usable on the first line of Program.cs
Get and set global properties via JS.Set and JS.Get
Create new Javascript objects with JS.New
Get and set object properties via IJSInProcessObjectReference extended methods
Create Callbacks that can be sent to Javascript event listeners or assigned to javascript variables
JS
// Get Set
var innerHeight = JS.Get<int>("window.innerHeight");
JS.Set("document.title", "Hello World!");
// Call
var item = JS.Call<string?>("localStorage.getItem", "itemName");
JS.CallVoid("addEventListener", "resize", Callback.Create(() => Console.WriteLine("WindowResized"), _callBacks));
IJSInProcessObjectReference extended
// Get Set
var window = JS.Get<IJSInProcessObjectReference>("window");
window.Set("myVar", 5);
var myVar = window.Get<int>("myVar");
// Call
window.CallVoid("addEventListener", "resize", Callback.Create(() => Console.WriteLine("WindowResized")));
Create a new Javascript object
var worker = JS.New("Worker", myWorkerScript);
Pass callbacks to Javascript
JS.Set("testCallback", Callback.Create<string>((strArg) => {
Console.WriteLine($"Javascript sent: {strArg}");
// this prints "Hello callback!"
}));
// in Javascript
testCallback('Hello callback!');
JSObject
JSObjects are wrappers around IJSInProcessReference objects that can be passed to and from Javascript and allow strongly typed access to the underlying object.
Use the extended functions of IJSInProcessObjectReference to work with Javascript objects or use the growing library of over 100 of the most common Javascript objects, including ones for Window, HTMLDocument, WebStorage (localStorage and sessionStorage), WebGL, WebRTC, and more in SpawnDev.BlazorJS.JSObjects. JSObjects are wrappers around IJSInProcessObjectReference that allow strongly typed use.
Custom JSObjects
Implement your own JSObject classes for Javascript objects not already available in the BlazorJS.JSObjects library.
Instead of this (simple but not as reusable)
var audio = JS.New("Audio", "https://some_audio_online");
audio.CallVoid("play");
You can do this...
Create a custom JSObject wrapper
[JsonConverter(typeof(JSObjectConverter<Audio>))]
public class Audio : JSObject
{
public Audio(IJSInProcessObjectReference _ref) : base(_ref) { }
public Audio(string url) : base(JS.New("Audio", url)) { }
public void Play() => JSRef.CallVoid("play");
}
Then use your new object
var audio = new Audio("https://some_audio_online");
audio.Play();
Promise
Below is a an example that uses Promises to utilize the Web Locks API
using var navigator = JS.Get<Navigator>("navigator");
using var locks = navigator.Locks;
Console.WriteLine($"lock: 1");
using var waitLock = locks.Request("my_lock", Callback.CreateOne((Lock lockObj) => new Promise(async () => {
Console.WriteLine($"lock acquired 3");
await Task.Delay(5000);
Console.WriteLine($"lock released 4");
})));
using var waitLock2 = locks.Request("my_lock", Callback.CreateOne((Lock lockObj) => new Promise(async () => {
Console.WriteLine($"lock acquired 5");
await Task.Delay(5000);
Console.WriteLine($"lock released 6");
})));
Console.WriteLine($"lock: 2");
SpawnDev.BlazorJS.WebWorkers
Easily call Blazor Services in separate threads with WebWorkers and SharedWebWorkers
Does not require SharedArrayBuffer and therefore does not require the special HTTP headers associated with using it.
Supports and uses transferable objects whenever possible
Works in Blazor WASM .Net 6, 7, and 8.
Tested on (with .Net 8):
Chrome Windows - Working
MS Edge Windows - Working
Firefox Windows - Working
Chrome Android - Working
MS Edge Android - Working
Firefox Android - Working
Firefox WebWorkers note:
Firefox does not support dynamic modules in workers, which originally made BlazorJS.WebWorkers fail in that browser.
The web worker script now tries to detect this and changes the blazor wasm scripts before they are loaded to workaround this limitation. It is possible some other browsers may have this issue but may not be detected properly.
// Program.cs
...
using SpawnDev.BlazorJS;
using SpawnDev.BlazorJS.WebWorkers;
var builder = WebAssemblyHostBuilder.CreateDefault(args);
if (JS.IsWindow)
{
// we can skip adding dom objects in non UI threads
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");
}
// add services
builder.Services.AddSingleton((sp) => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
// SpawnDev.BlazorJS.WebWorkers
builder.Services.AddSingleton<WebWorkerService>();
// app specific services...
// worker services should be registered with an interface to work with WebWorker.GetService<TServiceInterface>()
builder.Services.AddSingleton<IMathsService, MathsService>();
// build
WebAssemblyHost host = builder.Build();
// init WebWorkerService
var workerService = host.Services.GetRequiredService<WebWorkerService>();
await workerService.InitAsync();
await host.RunAsync();
WebWorker
// Create a WebWorker
var webWorker = await workerService.GetWebWorker();
// Call GetService<ServiceInterface> on a web worker to get a proxy for the service on the web worker.
// GetService can only be called with Interface types
var workerMathService = webWorker.GetService<IMathsService>();
// Call async methods on your worker service
var result = await workerMathService.CalculatePi(piDecimalPlaces);
// Action types can be passed for progress reporting
var result = await workerMathService.CalculatePiWithActionProgress(piDecimalPlaces, new Action<int>((i) =>
{
// the worker thread can call this method to report progress if desired
piProgress = i;
StateHasChanged();
}));
SharedWebWorker
Calling GetSharedWebWorker in another window with the same sharedWorkerName will return the same SharedWebWorker
// Create or get SHaredWebWorker with the provided sharedWorkerName
var sharedWebWorker = await workerService.GetSharedWebWorker("workername");
// Just like WebWorker but shared
var workerMathService = sharedWebWorker.GetService<IMathsService>();
// Call async methods on your shared worker service
var result = await workerMathService.CalculatePi(piDecimalPlaces);
Send events
// Optionally listen for event messages
worker.OnMessage += (sender, msg) =>
{
if (msg.TargetName == "progress")
{
PiProgress msgData = msg.GetData<PiProgress>();
piProgress = msgData.Progress;
StateHasChanged();
}
};
// From SharedWebWorker or WebWorker threads send an event to connected parents
workerService.SendEventToParents("progress", new PiProgress { Progress = piProgress });
// Or on send an event to a connected worker
webWorker.SendEvent("progress", new PiProgress { Progress = piProgress });
Worker Transferable JSObjects
Faster is better. SpawnDev WebWorkers use transferable objects by default for better performance, but it can be disabled with WorkerTransferAttribute. Setting WorkerTransfer to false will cause the property, return value, or parameter to be copied to the receiving thread instead of transferred.
Example
public class ProcessFrameResult : IDisposable
{
[WorkerTransfer(false)]
public ArrayBuffer? ArrayBuffer { get; set; }
public byte[]? HomographyBytes { get; set; }
public void Dispose(){
ArrayBuffer?.Dispose();
}
}
[return: WorkerTransfer(false)]
public async Task<ProcessFrameResult?> ProcessFrame([WorkerTransfer(false)] ArrayBuffer? frameBuffer, int width, int height, int _canny0, int _canny1, double _needlePatternSize)
{
var ret = new ProcessFrameResult();
// ...
return ret;
}
In the above example; the WorkerTransferAttribute on the return type set to false will prevent all properties of the return type from being transferred.
Inspired by Tewr's BlazorWorker implementation. Thank you! I wrote my implementation from scratch as I needed workers in .Net 7. https://github.com/Tewr/BlazorWorker
