Type extensions

TypeExtensions.cs

static class TypeExtensions
{
    public static IEnumerable<Type> GetInstanceTypesImplementing<T>(
        this Assembly assembly, params Assembly[] assemblies)
    {
        var serviceType = typeof(T);
        return assemblies.Union(new [] { assembly }).SelectMany(x => x.GetTypes())
            .Where( x => x.IsClass && !x.IsAbstract && serviceType.IsAssignableFrom( x ) );
    }

    public static IEnumerable<Type> GetTypesDecoratedWith<T>(
        this Assembly assembly, params Assembly[] assemblies ) where T : Attribute
    {
        var decoratorType = typeof(T);
        return assemblies.Union(new [] { assembly }).SelectMany(x => x.GetTypes())
            .Where( x => x.IsClass && !x.IsAbstract && x.GetCustomAttributes(decoratorType, true ).Any());
    }
    
    public static bool ImplementsGenericInterface(
        this Type typeToInspect, Type genericInterface)
        => genericInterface.IsGenericTypeDefinition is false
            ? throw new InvalidOperationException( $"Expected type '{genericInterface}' to be a generic type definition" )
            : typeToInspect
                .GetInterfaces()
                .Any( x => x.IsGenericType && x.GetGenericTypeDefinition() == genericInterface );
}