c# 3.0 - Unexpected C# behaviour with autoproperties and constructors -

it took me debugging figure out (or think). let code loose on , see come with. there simple contact class with:

1. some auto-properties,
2. a parameterized constructor increments contact.id property , sets other properties according arguments gets
3. a parameterless constructor calls parameterized constructor default values.

first see code; output , question follows code:

 using system;   class program   {    private static void main(string[] args)     {       contact[] contacts_array = {           //contact 0          new contact(),           //contact 1          new contact {             name = "contactname1",             age = 40,             email = "emailaddress1@email.com"          },           //contact 2          new contact {             name = "contactname2",             age = 41,             email = "emailaddress2@email.com"          },           //contact 3          new contact("contactname3",             42,             "emailaddress3@email.com"),       };        foreach (var contact in contacts_array)          console.writeline(contact);        console.readline();    } }  public class contact {     public static int totalcontacts = 0;     public int id { get; private set; }     public string name { get; set; }     public int? age { get; set; }     public string email { get; set; }      public contact()     {           new contact("anonymous", null, "anonymous@unknown.com");       }      public contact(string name, int? age, string email)     {         id = contact.totalcontacts++;         name = name;         age = age;         email = email;     }      public override string tostring()     {         return string.format("[contact: id={0}, name={1}, age={2}, email={3}]",                              id, name, age, email);     } } 

output:

[contact: id=0, name=, age=, email=]   [contact: id=0, name=contactname1, age=40, email=emailaddress1@email.com]   [contact: id=0, name=contactname2, age=41, email=emailaddress2@email.com]   [contact: id=3, name=contactname3, age=42, email=emailaddress3@email.com]  

question:

why contact.id == 0 in second , third contacts rather being 1 , 2 respectively, despite parameterized constructor being called , increment id property?

your default constructor doesn't think does:

public contact() {     new contact("anonymous", null, "anonymous@unknown.com"); } 

this construct new contact , discard it, current instance default values. here syntax you're after:

public contact()   : this("anonymous", null, "anonymous@unknown.com") { }