C# Reflection Check for Implemented Interface UWP

So i try to create a PluginService which loads assemblys from a folder and checks if it implements a certain interface. I work with the Interface

public interface IService
    {
        void Start();
        void Stop();
        void Restart();
    }

And the Class

public class Service : IService
    {

        public Service()
        {

        }

        public void Restart()
        {

        }

        public void Start()
        {

        }

        public void Stop()
        {

        }
    }

And i found this Question from pogorman which helped me a lot. But every time the DoesTypeImplementInterface method checks for the Inferface, it returns false.