Squeezing More Performance from SortedList

using System;
namespace SplitArrayDictionary
{

    /// <summary>
    /// Summary description for Class1
    /// </summary>
    public class StubDictionary<TValue>
        : System.Collections.Generic.IDictionary<int, TValue>
    {
        #region IDictionary<int,TValue> Members
        TValue lastValue;
        int lastint;
        public void Add(int key, TValue value)
        {
            lastValue = value;
            lastint = key;
        }

        public bool ContainsKey(int key)
        {
            if (key == lastint) return true;
            throw new NotImplementedException();
        }

        public System.Collections.Generic.ICollection<int> Keys
        {
            get { throw new NotImplementedException(); }
        }

        public bool Remove(int key)
        {
            throw new NotImplementedException();
        }

        public bool TryGetValue(int key, out TValue value)
        {
            if (key == lastint)
            {
                value = lastValue;
                return true;
            }

            throw new NotImplementedException();
        }

        public System.Collections.Generic.ICollection<TValue> Values
        {
            get { throw new NotImplementedException(); }
        }

        public TValue this[int key]
        {
            get
            {
                if (key == lastint)
                {
                    return lastValue;
                }

                throw new NotImplementedException();
            }
            set
            {
                this.lastint = key;
                this.lastValue = value;
            }
        }

        #endregion

        #region ICollection<KeyValuePair<int,TValue>> Members

        public void Add(System.Collections.Generic.KeyValuePair<int, TValue> item)
        {
            throw new NotImplementedException();
        }

        public void Clear()
        {
            this.lastint = 0;
            this.lastValue = default(TValue);
        }

        public bool Contains(System.Collections.Generic.KeyValuePair<int, TValue> item)
        {
            throw new NotImplementedException();
        }

        public void CopyTo(System.Collections.Generic.KeyValuePair<int, TValue>[] array, int arrayIndex)
        {
            throw new NotImplementedException();
        }

        public int Count
        {
            get { return -1; }
        }

        public bool IsReadOnly
        {
            get { throw new NotImplementedException(); }
        }

        public bool Remove(System.Collections.Generic.KeyValuePair<int, TValue> item)
        {
            throw new NotImplementedException();
        }

        #endregion

        #region IEnumerable<KeyValuePair<int,TValue>> Members

        public System.Collections.Generic.IEnumerator<System.Collections.Generic.KeyValuePair<int, TValue>> GetEnumerator()
        {
            throw new NotImplementedException();
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            throw new NotImplementedException();
        }

        #endregion
    }
}