I’m working on creating my own dependency injection framework in C# as a learning exercise. However, I’m encountering an issue when trying to get the primary constructor of a class from its type.

Here is what I’ve tried:

public class HelloService(MessageService service)
{
    public void Print()
    {
        Console.WriteLine("Hello " + service.Message());
    }
}

public class Dependency(Type type, DependencyLifetime lifetime)
{
    public DependencyLifetime Lifetime { get; set; } = lifetime;
    public Type Type { get; set; } = type;
    public object Instance { get; set; } 
    public bool Initialized { get; set; } = false;
}

    public T GetService<T>()
    {
        return (T) GetService(typeof(T));
    }

    public object GetService(Type type)
    {
        var dependency = _container.GetDependency(type);

        var constructors = type.GetConstructors();
        var constructor = constructors.First();
        var parameters = constructor.GetParameters();

        if (parameters.Length > 0)
        {
            var parameterImplementations = new object[parameters.Length];
            for (int i = 0; i < parameters.Length; i++)
            {
                parameterImplementations[i] = GetService(parameters[i].ParameterType);
            }

            return CreateImplementation(dependency, () => constructor.Invoke(parameterImplementations));
        }

        return CreateImplementation(dependency, () => Activator.CreateInstance(type));
    }

    public object CreateImplementation(Dependency dependency, Func <Object> factory)
    {
        if (dependency.Initialized)
        {
            return dependency.Instance;
        }

        var implementation = factory();

        if (dependency.Lifetime == DependencyLifetime.Transient)
        {
            return implementation;
        }

        dependency.Initialized = true;
        dependency.Instance = implementation;
        return implementation;
    }

Once I run this code, I get the following error:

Unhandled exception. System.InvalidOperationException: Sequence contains no elements
at System.Linq.ThrowHelper.ThrowNoElementsException()
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)

In the debugger I tried looking at the properties of type, but I couldn’t find anything for the primary constructor. Is there a way to find primary constructor, so my code works without declaring the normal constructor.