MultiTerm/Common/StartupHelpers/ServiceExtensions.cs

using Microsoft.Extensions.DependencyInjection;

namespace Common.StartupHelpers;

public static class ServiceExtensions
{
    /// <summary>
    /// Service Extension to add an <see cref="AbstractFactory{T}"/> to Dependency Injection.
    /// </summary>
    /// <typeparam name="TInterface">Type of interface</typeparam>
    /// <typeparam name="TImplementation">Type of implementation</typeparam>
    /// <param name="services">existing service collection</param>
    public static void AddAbstractFactory<TInterface, TImplementation>(this IServiceCollection services)
        where TInterface : class
        where TImplementation : class, TInterface
    {
        // add implementation to services collection
        services.AddTransient<TInterface, TImplementation>();
        // add factory function to services collection
        services.AddSingleton<Func<TInterface>>(x => () => x.GetService<TInterface>()!);
        // add factory implementation to services collection
        services.AddSingleton<IAbstractFactory<TInterface>, AbstractFactory<TInterface>>();
    }

    /// <summary>
    /// Adds a factory for subcontrols to be created.
    /// For example a UserControl can be instanciated using this Service.
    /// </summary>
    /// <typeparam name="TSubControl">type of the subcontrol</typeparam>
    /// <param name="services">existing service collection</param>
    public static void AddSubControlFactory<TSubControl>(this IServiceCollection services) where TSubControl : class
    {
        // add to DI: the subcontrol itself
        services.AddTransient<TSubControl>();
        // add to DI: Func of constructor of that subcontrol
        services.AddSingleton<Func<TSubControl>>(x => () => x.GetService<TSubControl>()!);
        // add to DI: Factory for the subcontrol
        services.AddSingleton<IAbstractFactory<TSubControl>, AbstractFactory<TSubControl>>();
    }
}