public class Parent
{
  private bool _isChanged;

  public IList<Child> Children { get; set; }

  public bool IsChanged
  {
    get
    {
      return _isChanged || Children.Exists(c => c.IsChanged);
    }
    set { _isChanged = value; }
  }
}

public class Child
{
  public bool IsChanged { get; set; }
}