What am I doing wrong with C# object initializers?

Question

When i initialize an object using the new object initializers in C# I cannot use one of the properties within the class to perform a further action and I do not know why.

My example code:

Person person = new Person { Name = "David", Age = "29" };

Within the Person Class, x will equal 0 (default):

public Person()
{
  int x = Age; // x remains 0 - edit age should be Age. This was a typo
}

However person.Age does equal 29. I am sure this is normal, but I would like to understand why.

Answer 1

The properties get set for Name and Age after the constructor 'public Person()' has finished running.

Person person = new Person { Name = "David", Age = "29" };

is equivalent to

Person tempPerson = new Person()
tempPerson.Name = "David";
tempPerson.Age = "29";
Person person = tempPerson;

So, in the constructor Age won't have become 29 yet.

(tempPerson is a unique variable name you don't see in your code that won't clash with other Person instances constructed in this way. tempPerson is necessary to avoid multi-threading issues; its use ensures that the new object doesn't become available to any other thread until after the constructor has been executed and after all of the properties have been initialized.)

---

If you want to be able to manipulate the Age property in the constructor, then I suggest you create a constructor that takes the age as an argument:

public Person(string name, int age)
{
   Name = name;
   Age = age;

   // Now do something with Age
   int x = Age;
   // ...
}