GUID Tree Data Structure

// Author: Trevy
//
namespace TrevyCo.Tools
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Collections;
    using System.Runtime.Serialization;

    /// <summary>
    /// It uses computer memory to store data for memory usage under 1 MG
    /// Above that, it switches to using computer storage as a medium
    /// </summary>
    public class GuidCollection<T>
    {
        #region Data
        private GuidTreeBase<T> guidTree;

        public long Count
        {
            get
            {
                return count;
            }
        }
        private long count = 0; 
        #endregion

        #region Constructors
        /// <summary>
        /// Uses computer memory exclusively.
        /// </summary>
        /// <remarks>
        /// Can slow computer if too many entries added
        /// </remarks>
        public GuidCollection(bool overwriteValues = false)
        {
            guidTree = new GuidArrayTree<T>();
            guidTree.OverwriteValues = overwriteValues;
        }

        /// <summary>
        /// Uses computer memory to store data for memory usage under 1 MG
        /// Above that, it switches to using computer storage as a medium
        /// </summary>
        /// <param name="scratchArea">Area to store data.</param>
        /// <remarks>
        /// WARNING: Choose a secure are with sufficient memory to store all the data you need to add
        /// </remarks>
        public GuidCollection(string scratchArea, bool overwriteValues = false)
        {
            Attribute attribute = Attribute.GetCustomAttribute(typeof(T), typeof(System.SerializableAttribute));
            if (attribute == null)
            {
                throw new ApplicationException(typeof(T).Name + " must have the System.Serializable Attribute, since we are storing the value in the file system.");
            }

            guidTree = new GuidFileTree<T>(scratchArea);
            guidTree.OverwriteValues = overwriteValues;
        } 
        #endregion

        #region Public methods
        /// <summary>
        /// Add key, value pair to dictionary
        /// </summary>
        public void Add(Guid key, T val)
        {
            if (guidTree.Add(key, val))
            {
                count++;
            }
        }

        /// <summary>
        /// Set weather we can overwrite existing values
        /// </summary>
        public bool OverwriteValues
        {
            get
            {
                return guidTree.OverwriteValues;
            }
            set
            {
                guidTree.OverwriteValues = value;
            }
        }

        /// <summary>
        /// Index into collection
        /// </summary>
        /// <param name="key">GUID</param>
        /// <returns>the value</returns>
        public T this[Guid key]
        {
            get
            {
                T val;
                if (TryGetValue(key, out val))
                {
                    return val;
                }
                else
                {
                    throw new InvalidOperationException("Key doesn't exist");
                }
            }
            set
            {
                Add(key, value);
            }
        }

        /// <summary>
        /// Try to get the value
        /// </summary>
        /// <returns>True if vlue exists, false othervise</returns>
        public bool TryGetValue(Guid key, out T val)
        {
            return guidTree.TryGetValue(key, out val);
        }

        /// <summary>
        /// Can be time-consuming
        /// </summary>
        public void Clear()
        {
            guidTree.Clear();
            count = 0;
        }

        /// <summary>
        /// Remove item corresponding to the key
        /// </summary>
        /// <returns>true if value removed</returns>
        public bool Remove(Guid key)
        {
            bool res = guidTree.Remove(key);
            if (res)
            {
                count--;
            }

            return res;
        }

        /// <summary>
        /// Check if key exists
        /// </summary>
        /// <returns>true if key exists, false otherwise</returns>
        public bool ContainsKey(Guid key)
        {
            return guidTree.ContainsKey(key);
        }

        /// <summary>
        /// Gets the enummerator
        /// </summary>
        /// <returns>Enumerator</returns>
        public IEnumerable<T> GetEnumerator()
        {
            return guidTree.GetEnumerator();
        } 
        #endregion
    }
}