that doesn't work, but i think i have found my own answer:
ActiveDirectorySchema ass = ActiveDirectorySchema.GetCurrentSchema();
ActiveDirectorySchemaClass u = ass.FindClass("person");
foreach (ActiveDirectorySchemaProperty a in u.GetAllProperties())
Console.WriteLine(a.CommonName + " : " + a.Syntax);
i needed the "Syntax" so i could then know how to convert the data.
thank for your help