Lazy loading class

/// 

    /// Lazy loading class. When the value is required object will ask for item provider and cache result.
    /// 
    /// Item type.
    /// Key type.
    internal class LazyLoadingBase
    {
        public delegate TItem GetItemWithNameDelegate(TKey name);

        GetItemWithNameDelegate getItemWithName;

        TKey key;
        TItem item;
        bool itemSet;

        public LazyLoadingBase(GetItemWithNameDelegate GetItemWithName)
        {
            itemSet = false;
            item = default(TItem);
            getItemWithName = GetItemWithName;
        }

        public object Value 
        {
            get
            {                
                if (!itemSet)
                {
                    item = getItemWithName(key);
                    itemSet = true;
                }
                return item;
            }

            set
            {
                if (value is TItem)
                {
                    item = (TItem)value;
                    itemSet = true;
                }
                else if (value is TKey)
                {
                    key = (TKey)value;
                }
                else
                {
                    throw new InvalidOperationException();
                }
            }
        }

        /// 

        /// Cast operator.
        /// 
        
        public static implicit operator TItem(LazyLoadingBase lazyLoadingBaseObject)
        {
            return (TItem)lazyLoadingBaseObject.Value;            
        }       
   }