C# Cast object to generic interface with Type parameter

I want to cast an object as an generic custom Interface.

This is my interface:

public interface IContainer<T>
{
    IEnumerable<T> SaveToCache(IEnumerable<T> models);
}

I'm using this interface in a Serviceclass:

public class Manager()
{
    public Manager()
    {
        address = new Container<Address>(this);
        // more containers are constructed here...
    }

    private static Container<Address> address;
    public static Container<Address> Address => address;

    // here are more properties of Type Container<T>
}

Now I want to call the SaveToCacheAsync method dynamically like this:

private void SaveItems(IEnumerable<object> items, string typeName)
{
    object container = typeof(Manager)
        .GetRuntimeProperty(typeName).GetValue(null, null);
    var t = Type.GetType($"MyNameSpace.Models.{typeName}");

    // variant A - doesn't work, but makes clear what I want to do
    (container as IContainer<t>).SaveToCache(items);

    // variant B - doesn't work either
    var saveMethod = container.GetType()
        .GetRuntimeMethod("SaveToCache", new Type[] { Type.GetType($"System.Collections.Generic.List`1[{t.FullName}]") })
        .MakeGenericMethod(new Type[] { t });

    saveMethod.Invoke(container, new object[] { });
}

The project is a PCL, therefore I used GetRuntimeMethods.