Objects that become empty when passed to a property in C #

Question

I have an abstract class called Employee and two other classes that extend it (Developer and Manager). My problem is that when I create a Manager

Employee man = new Manager(1234567, 30, "Bob", "Pie") 

and try installing it in the "Manager" field of the new developer,

 Employee codemonkey = new Developer(1234568, 20, "Code", "Monkey", (Manager)man) 

I keep getting ArgumentException that my manager is null. I made some checks, and it somehow becomes null when I try to set it with the Manager property in the constructor. Any advice as to why I am getting this error would be greatly appreciated. TIA!

Code for each below:

// Class of employees

 public abstract class Employee { string firstName, lastName; int id, yearsEmployed; //Names must be non-empty public string FirstName { get { return firstName; } set { if (!value.Equals("")) { firstName = value; } else throw new ArgumentException("name cannot be empty"); } } public string LastName { get { return lastName; } set { if (!value.Equals("")) { lastName = value; } else throw new ArgumentException("name cannot be empty"); } } // IDs must be strings consisting of exactly seven digits. public int ID { get { return id; } set { if (value.ToString().Length == 7) { id = value; } else throw new ArgumentException("ID must consist of 7 digits"); } } // Years employed must always be non-negative. public int YearsEmployed { get { return yearsEmployed; } set { if (value >= 0) { yearsEmployed = value; } else throw new ArgumentException("Year employed must be non-negative"); } } //Constructor public Employee(int id, int yearsEmployed, string firstName, string lastName) { this.FirstName = firstName; this.LastName = lastName; this.ID = id; this.YearsEmployed = yearsEmployed; } public abstract int GetLevel { get; } public abstract string GetTitle { get; } public string GetFullTitle { get { return GetTitle + " " + GetLevel; } } } 

// Developer class:

  public class Developer : Employee { Manager manager; //Manager cannot be null public Manager Manager { get { return manager; } set { if (manager != null) { manager = value; } else throw new ArgumentException("Manager cannot be null"); } } //Constructor public Developer(int id, int yearsEmployed, string firstName, string lastName, Manager manager) : base(id, yearsEmployed, firstName, lastName) { Console.WriteLine("manager is not null:" + manager != null); //True here this.Manager = manager; // manager is null here } public override int GetLevel { get { return (this.YearsEmployed + 1) / 3; } } public override string GetTitle { get { return "Developer"; } } } 

// Manager class

 public class Manager : Employee { //Constructor public Manager(int id, int yearsEmployed, string firstName, string lastName) : base(id, yearsEmployed, firstName, lastName) { } public override int GetLevel { get { return (YearsEmployed + 1) / 2; } } public override string GetTitle { get { return "Manager"; } } } 

Answer 1

Do you want to say:

 if (value != null) 

instead

 if (manager != null) 

The manager field will be initialized to zero. The value keyword represents the data passed to this property.

Answer 2

Change

  if (manager != null) 

For

  if (value != null) 

Answer 3

you never set the value of the field manager, but only the property manager, so in the property when you check the value of the manager, it is null because it has not been set. you can set the field manager in the constructor:

 this.manager=manager 

and check the value in the property

 if (value!=null) { manager =value; } 

(you still need to do this, otherwise the value you give to this property will never be used and will never be updated)

depending on whether you want the Manager to be changed.

Answer 4

In the change of developer Developer.Manager

 if (manager != null) 

to

 if (value != null)