Cannot implicitly convert type 'customtype' to 'othercustomtype'

Question

I am new to C#. I have a Persons class and a User class which inherits from the Persons class. I my console I input a users in an array. Then I can add a note to a user that

Answer 1

Since User inherits from Person, you cannot implicitly convert any random Person to a User (though you can implicitly convert a User to a Person).

Since you pass a User[] to FindPerson(users, id), you can be sure the returned person is indeed a User, so you can cast it like this:

return (User)person;

Edit: You might consider using generics on FindPerson to avoid the cast altogether.

public static T FindPerson(IEnumerable persons, int noteid)
    where T : Person
{
    foreach (T person in persons)
    {
        if (person.ID == noteid)
        {
            return person;
        }
    }

    return null;
}

public static User SelectUser(User[] users)
{
    while (true)
    {
        Console.Write("Please enter the User id: ");
        string input = Console.ReadLine();
        int id;
        if (int.TryParse(input, out id))
        {
            User person = Persons.FindPerson(users, id);
            if (person != null)
            {
                return person;
            }            
        }

        Console.WriteLine("The User does not exist. Please try again.");                
    }
}