About TwoWay Binding in SilverLight.

public class MyProduct : INotifyPropertyChanged
    {
        private Dictionary<string, object> _properties = new Dictionary<string, object>();

        protected virtual T GetValue<T>(string name)
        {
            if (this._properties.ContainsKey(name))
                return (T)this._properties[name];

            return default(T);
        }

        protected virtual void SetValue<T>(string name, T value)
        {
            bool set = false;
            if (!this._properties.ContainsKey(name))
            {
                this._properties.Add(name, value);
                set = true;
            }
            else if (!object.Equals(this._properties[name], value))
            {
                this._properties[name] = value;
                set = true;
            }
            if (set)
            {
                this.NotifyChange(name);
            }
        }

        protected virtual void NotifyChange(params string[] properties)
        {
            if (PropertyChanged != null)
            {
                foreach (string p in properties)
                    PropertyChanged(this, new PropertyChangedEventArgs(p));
            }
        }
        #region INotifyPropertyChanged Members
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }

Mode="TwoWay"