如何在整个应用程序中创建和注入用户特定的 singleton class？

Question

I'm trying to create a user-specific specific singleton object on Blazor serverside application. Is there a way we can achieve this using .NET Core dependency injection system? I've tried below code. I've created SingletonTest class.

public class SingletonTest
{
    private int _counter;
    public int Counter { get { return ++_counter; } }
}

Injected the SingletonTest class in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<SingletonTest>();
}

Accessing the Counter property in index.razor file

@page "/"
@inject SingletonTest singletonTest;
Counter: @singletonTest.Counter

When I try to access the index page in two different browsers, both are accessing the same single instance of SingletonTest class. I there a way I can make this user-specific singleton? once the browser is closed the server need to dispose the user-specific singleton object and call the garbage collector.

Answer 1

Add Scoped is what you need if you want it to be only available to a single browser instance:

services.AddScoped<YourScopedClass>();

Another thing you can use is a preview Nuget package:

Microsoft.AspNetCore.ProtectedBrowserStorage

the docs for ProtectedBrowserStorage are are about 40% down on this page: https://docs.microsoft.com/en-us/aspnet/core/blazor/state-management?view=aspnetcore-3.1

I use the above package here in a Server Side Blazor project called BlazorChat that uses a singleton just like you are to communicate to all the users, but the ProtectedBrowserStorage to store the users password hash, email address and login name.

https://github.com/DataJuggler/BlazorChat

The site is also live, but no one has signed up but me so far.

https://blazorchat.com