readme.md

Service Provider Proof of Concept (PoC)

This library is a PoC to see if dynamic (child) service providers can be used.

Requirements

When using the dependency injection extensions from Microsoft, all the services has to be known upfront. This is a great way to build up an application.

Some applications require dynamic service registrations where multiple services with a different key (scope) must run side-by-side. Although the service collection supports keyed registrations, the keys must be known upfront. A few use cases where this is not possible are:

• Workspaces
• Filters
• Multi document interface (MDI)

Instead of having to manage keyed state in every service, this PoC supports creating (and disposing) runtime service collections with a corresponding service provider.

Implementation

Registering a scope

To register a new scope, the application must use IServiceScopeManager.AddScope(ScopeContext context):

var scope = _scopeManager.AddScope(new ServiceScopeContext
{
    Id = "TestScope",
    DisposeScopeServices = true,
});

Registering services for a scope

To register services for a dynamic / runtime scope, the application must register one or more types implementing IScopeServiceCollectionProvider.

Example implementation:

internal class ScopeServiceCollectionProvider : IScopeServiceCollectionProvider
{
    private readonly ILogger<ScopeServiceCollectionProvider> _logger;

    public ScopeServiceCollectionProvider(ILogger<ScopeServiceCollectionProvider> logger)
    {
        _logger = logger;
    }

    public IServiceCollection AddServices(IServiceCollection serviceCollection, string? scopeId)
    {
        _logger.LogInformation("Adding services for scope '{ScopeId}'", scopeId);

        serviceCollection.TryAddSingleton<IFilterService, FilterService>();

        return serviceCollection;
    }
}

Then the class must be registered during the program registrations:

serviceCollection.AddSingleton<IScopeServiceCollectionProvider, ScopeServiceCollectionProvider>();

If ScopeContext.IsIsolated is not set the true, all services registered in the parent IServiceProvider will automatically be added to the child service collection as well.

Using the scope

To use runtime scopes, use the following code:

var scope = scopeManager.GetScope("TestScope");
if (scope is not null)
{
    var scopedService = scope.ServiceProvider.GetRequiredService<IFilterServce>();
}

Types can also be constructed using ActivatorUtilities:

var scope = scopeManager.GetScope("TestScope");
if (scope is not null)
{
    var scopedObject = ActivatorUtilities.CreateInstance<MyObject>(scope.ServiceProvider);
}

Removing a scope

To remove a scope, call IServiceScopeManager.RemoveScope(string id).

This will remove the scope and, optionally, dispose the explicitly registered services or service provider.