CustomAttribute error on assembly getTypeInfo

Question

I've got a c# static class which does:

public static class AssStaticHelp
    {
       
        static private List<Type> Tipi=new List<Type>();
        public static string searchManagerMethod = @"C:\StoredWeb\StoredWeb\searchManagerMethod";

        public static List<Type> GetTipi()
        {
            AppDomain currDomain = AppDomain.CurrentDomain;
            currDomain.ReflectionOnlyAssemblyResolve += new ResolveEventHandler(HandlerMethodTipi);

            if (currDomain.ReflectionOnlyGetAssemblies().Length == 0)
                Tipi = new List<Type>();

            if (Tipi.Count == 0) {
                currDomain.ReflectionOnlyAssemblyResolve += new ResolveEventHandler(HandlerMethodTipi);
                DirectoryInfo di = new DirectoryInfo(searchManagerMethod);
                foreach (FileInfo f in di.GetFiles("*.dll"))
                {
                    Assembly ass = Assembly.ReflectionOnlyLoadFrom(f.FullName);
                    Type[] listType = ass.GetTypes();
                    if (listType.Length > 0)
                    {
                        Tipi.AddRange(listType);
                    }
                }

            }

            return Tipi;
        }
     

        private static Assembly HandlerMethodTipi(object sender, ResolveEventArgs args)
        {
            AssemblyName assName = new AssemblyName(args.Name);
            string fileName = Path.GetFullPath(searchManagerMethod + "\\" + assName.Name + ".dll");
            if (File.Exists(fileName))
            {

                return Assembly.ReflectionOnlyLoadFrom(fileName);
            }
            return Assembly.ReflectionOnlyLoad(args.Name);
        }

Essentially it loads some assembly I need to explore when a custom attribute (SialBaseType) is set, like this:

[Serializable]
    [SialBaseType("SialMinBaseType", true)]
    public abstract class SialMinBaseType : BEBase
    {
        #region Property
        /// <summary>
        /// Identificativo univoco dell'oggetto
        /// </summary>
        public string Id { get; set; }
...

the problem is sometimes I can get the custom attribute data, sometimes not...and I can't figure out why...

here's the situation:

1. correct one:

2. the problem which gives me "Method not found: 'Void NETA.SUITE.SIAL.Tipi.Base.SialBaseTypeAttribute..ctor(System.String)'.":