Chain function calls using Excel-Dna

Question

Is it possible to chain function calls using Excel-Dna?

I am trying to call something like this from Excel Sheet:

=CreateAccount(CreateUser("John","Doe"))

But the inner function CreateUser returns ExcelErrorValue.

Demo C# code looks like this:

namespace ExcelDnaDemo
{
    using ExcelDna.Integration;

    public static class MyFunctions
    {
        [ExcelFunction(Description = "C-U")]
        public static object CreateUser(string firstName, string lastName)
        {
            return new User(firstName, lastName);
        }

        [ExcelFunction(Description = "C-A")]
        public static string CreateAccount(
            [ExcelArgument(
                Name = "Usr",
                Description = "User test", AllowReference = true)]
            object user)
        {
            var a = new Account(user);
            return $"{a.User.FirstName} {a.User.LastName} {a.Id}";
        }
    }

    public class User
    {
        public User(string firstName, string lastName)
        {
            FirstName = firstName;
            LastName = lastName;
        }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

    public class Account
    {
        public object User { get; private set; }
        public Guid Id { get; private set; }
        public Account(object user)
        {
            User = user;
            Id = Guid.NewGuid();
        }
    }
}

Answer 1

You might add the new user to an internal Dictionary<string, User> and return some kind of key, e.g. "User:1" from the CreateUser function. Then in CreateAccount you take in the string key, and check if it is present in the dictionary to retrieve the cached User object.