using System.Collections.Generic;
public class MyClassCollection : IEnumerable<MyClass>
{
    private List<MyClass> _Items = new List<MyClass>();
    private Dictionary<object, int> _Key = new Dictionary<object, int>();
    public int IndexOf(MyClass item)
    {
        return _Items.IndexOf(item);
    }
    public bool Contains(string key)
    {
        return _Key.ContainsKey(key);
    }
    public bool Contains(MyClass item)
    {
        return _Items.Contains(item);
    }
    public MyClass this[int i]
    {
        get
        {
            if (i >= 0 && i < Count)
            {
                return _Items[i];
            }
            else
            {
                return null;
            }
        }
    }
    public MyClass this[object key]
    {
        get
        {
            if (_Key.ContainsKey(key))
            {
                return _Items[_Key[key]];
            }
            else
            {
                return null;
            }
        }
    }
    public string CommandString { get; set; }
    public bool Add(MyClass item)
    {
        if (_Items.Contains(item))
            return false;
        _Key.Add(item.Key.Trim().ToLower(), _Items.Count);
        _Items.Add(item);
        return true;
    }
    public bool Remove(object key)
    {
        if (_Key.ContainsKey(key) == false)
            return false;
        return this.RemoveAt(_Key[key]);
    }
    public bool Remove(MyClass item)
    {
        if (_Items.Contains(item) == false)
            return false;
        return this.RemoveAt(_Items.IndexOf(item));
    }
    public bool RemoveAt(int i)
    {
        if (i < 0 || i > _Items.Count - 1)
            return false;
        _Key.Remove(_Items[i].Key);
        _Items.RemoveAt(i);
        if (i < _Items.Count)
        {
            for (int j = i; j <= _Items.Count - 1; j++)
            {
                _Key[_Items[j].Key.Trim().ToLower()] = j;
            }
        }
        return true;
    }
    public void Clear()
    {
        _Items.Clear();
        _Key.Clear();
    }
    public int Count
    {
        get { return _Items.Count; }
    }

    public System.Collections.Generic.IEnumerator<MyClass> GetEnumerator()
    {
        return _Items.GetEnumerator();
    }

    public System.Collections.IEnumerator GetEnumerator1()
    {
        return GetEnumerator();
    }
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator1();
    }
}
public class MyClass
{
    public string Key { get; set; }
    public string Value1 { get; set; }
    public string Value2 { get; set; }
    public string Value3{ get; set; }
}

------解决方案--------------------
HashTable、Dictionary，
.net3.5还有HashSet这种。