How do convert c++ dll to array byte and get it's methods in c#?

I have a c++ dll and I need to have it's methods in my c# app. but I can't get all methods in that dll. this is my code:

        byte[] data = File.ReadAllBytes(@"C:\ODSSwitchFunctions.dll");
        var result = data.GetType();

        foreach (Type type in result.Assembly.GetTypes())
        {
            if (!type.IsPublic)
            {
                continue;
            }

            MemberInfo[] members = type.GetMethods();

            foreach (MemberInfo member in members)
            {
                Console.WriteLine(member.Name);
            }
        }