在C＃中引发事件-需要帮助

Question

Hello I'm trying to raise an event when the Birthdate of a person is greater then the actual date.

I'm new with events and it doesn't seem to work.

Code is beneath,

namespace LibClassLuchthaven
{
    public class Person
    {

        public DateTime Birthdate { get; set; }

        public string Firstname { get; set; }
        public Gender Gender { get; set; }
        public string Name { get; set; }

        public event EventHandler BirthdateInFuture;

        public Person()
        {
            this.Birthdate = DateTime.Now;
            this.Firstname = string.Empty;
            this.Gender = Gender.unknown;
            this.Name = string.Empty;
        }
        public Person(DateTime birthdate, string firstname, Gender gender, string name)
        {
            this.Birthdate = birthdate;
            this.Firstname = firstname;
            this.Gender = gender;
            this.Name = name;
        }
        public void OnBirthdateInFuture()
        {

            if (BirthdateInFuture!=null)
            {
                if (this.Birthdate > DateTime.Now)
                {
                    BirthdateInFuture(this, EventArgs.Empty);
                }

            }

        }


        public override string ToString()
        {
            return  this.Name + ", " + this.Firstname + " - " + this.Birthdate + " ( +" + this.Gender + ")";
        }
    }
}

public partial class FormCrewManagement : Form
{

    public Person person = new Person();


    public FormCrewManagement()
    {
        InitializeComponent();

        person.BirthdateInFuture += Person_BirthdateInFuture;

    }

    private void Person_BirthdateInFuture(object sender, EventArgs e)
    {
        MessageBox.Show("Birthdate is in the future");
    }

Answer 1

Try Changing the Property

public DateTime Birthdate { get; set; }

to

private DateTime _birthDate;
public DateTime Birthdate 
{ 
   get {return _birthDate;} 
   set
   {
      _birthDate=value;
      if(value > DateTime.Now)
         BirthdateInFuture?.Invoke(this, EventArgs.Empty);
   } 
}

This will raise the event when Birthdate value is in future.

Answer 2

It looks like the problem may be a logical one, rather than anything to do with events. You are setting the birthday to today's date... then checking if it's later. It never will be.

public Person()
{
    this.Birthdate = DateTime.Now;

    if (BirthdateInFuture!=null)
    {
        if (this.Birthdate > DateTime.Now)
        {
            BirthdateInFuture(this, EventArgs.Empty);
        }
    }

Answer 3

Philip, there is no place in your code where the event is raised. You could create a property called BirthDate and in the setter part, raise the event. When the birthdate is changed to a future date, it would/could raise the event.