support decorating with a decorator interface

[akayyali]

support decorating with a decorator interface instead of concrete decorator, this will allow changing decorator concrete class without affecting business services implementation.
Example :

serviceCollection
    .AddTransient<ICommandHandler<CreateCityCommand>, CreateCityCommandHandler>()
    .AddTransient(typeof(ILogCommandHandler<>), typeof(LogCommandHandler<>))
    .AddTransient(typeof(IAuditCommandHandler<>), typeof(PrimaryAuditCommandHandler<>))

    .AddTransient(typeof(IService), typeof(MyService))
    .AddTransient(typeof(IMyServiceDecorator), typeof(AnotherServiceDecorator));

serviceCollection.Decorate<ICommandHandler<CreateCityCommand>, ILogCommandHandler<CreateCityCommand>>();
serviceCollection.Decorate<ICommandHandler<CreateCityCommand>, IAuditCommandHandler<CreateCityCommand>>();
serviceCollection.Decorate<IService, IMyServiceDecorator>();

[khellang]

This looks small enough that I'm willing to pull it into the library, but it's missing tests. Would you be able to add some?

[khellang]

Isn't typeof(TDecorator).IsGenericType always true here?

[khellang]

Could you add some braces while you're at it? I like to always use braces to avoid GOTO FAIL-type bugs 😉 https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/

[akayyali]

IsGenericType

not necessary, i`m taking into consideration here the interface could be either generic (IServiceDecorator < T > ) or not

[akayyali]

Could you add some braces while you're at it? I like to always use braces to avoid GOTO FAIL-type bugs 😉 https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/

totally, agree :)
thanks for pointing out

[khellang]

...and always false here? 🤔

[akayyali]

as per : https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.firstordefault?view=net-5.0
"The default value for reference and nullable types is null."