Working with ObservableCollection<T>

using ViewableCollectionDemo.ViewModels.ObjectModel;

namespace ViewableCollectionDemo.ViewModels.Application
{
    /// <summary>
    /// This class describes one contact, in a presentation-friendly manner.
    /// </summary>
    public class ContactViewModel : ObservableObject
    {
        private string _firstName = "New";
        /// <summary>
        /// This property stores the contact's first name.
        /// </summary>
        public string FirstName
        {
            get
            {
                return _firstName;
            }
            set
            {
                if (_firstName != value)
                {
                    _firstName = value;
                    base.RaisePropertyChanged("FirstName");
                }
            }
        }

        private string _lastName = "Contact";
        /// <summary>
        /// This property stores the contact's last name
        /// </summary>
        public string LastName
        {
            get
            {
                return _lastName;
            }
            set
            {
                if (_lastName != value)
                {
                    _lastName = value;
                    base.RaisePropertyChanged("LastName");
                }
            }
        }

        /// <summary>
        /// Returns a System.String representing this contact.
        /// </summary>
        /// <returns>A string formatted to have Last Name, First Name.</returns>
        public override string ToString()
        {
            return string.Format("{0}, {1}", this.LastName, this.FirstName);
        }

    }
}