using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data.Entity.Core.Metadata.Edm;
using System.Reflection;

namespace Ef_reflection
{
    class Program
    {
        static void Main(string[] args)
        {
            IList<EntitySetBase> newEntitySet = new List<EntitySetBase>();
            Type[] types = new Type[1];
            types[0] = newEntitySet.GetType();            
            ConstructorInfo ctor = typeof(ReadOnlyMetadataCollection<EntitySetBase>).GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance, null, types, null);
            Object[] p = new Object[1];
            p[0] = (object)newEntitySet;
            ReadOnlyMetadataCollection<EntitySetBase> internalCollection = ctor.Invoke(p);
        }
    }
}

Cannot implicitly convert type 'object' to 'System.Data.Entity.Core.Metadata.Edm.ReadOnlyMetadataCollection<System.Data.Entity.Core.Metadata.Edm.EntitySetBase>'. An explicit conversion exists (are you missing a cast?)