c＃通过设置成员值实例化一个类

Question

Currently when setting a member variable of on object I check if the object is instantiated. Is this really necessary, or is the object instantiated by just setting one member variable?

Person _Person;      

public int Age
{
  get
  {
    return _Person.Age;
  }
  set
  {
    if (_Person != null)
      _Person.Age = value;
    else
      _Person = new _Person(value);
  }
}

Is that the same as below?

Person _Person;      

public int Age
{
  get
  {
    return _Person.Age;
  }
  set
  {
    _Person.Age = value;
  }
}

Answer 1

No, you must instantiate to allocate the memory in the variable. With out instantiating the variable will be always equal to null

When an instance constructor has no constructor initializer, or it has a constructor initializer of the form base(...), that constructor implicitly performs the initializations specified by the variable-initializers of the instance fields declared in its class. This corresponds to a sequence of assignments that are executed immediately upon entry to the constructor and before the implicit invocation of the direct base class constructor.