KeyItem and KeyItemCollection

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.ComponentModel;

namespace Core
{
    /// <summary>
    /// Used to hold various key-value data
    /// </summary>
    [Serializable]
    [DebuggerDisplay("Key = {Key}, Value = {Value}")]
    public class KeyItem
    {
        string _key;
        string _value;

        public string Key
        {
            get { return _key; }
            set { _key = value; }
        }

        public string Value
        {
            get { return _value; }
            set { _value = value; }
        }

        public KeyItem() { }
        public KeyItem(string k, string v)
        {
            _key = k;
            _value = v;
        }
    }
       /// <summary>
    /// Collection of <seealso cref="KeyItem"/> objects that holds basic key-value data
    /// </summary>
    [Serializable]
    [DebuggerDisplay("Count = {Count}")]
    public class KeyItemCollection : List<KeyItem>
    {
        public bool TryGetValue(string key, out KeyItem item)
        {
            item = this.FirstOrDefault(t => t.Key == key);
            return item != null;
        }

        #region Indexer
        public string this[string key]
        {
            get
            {
                KeyItem kitem = null;
                if (this.TryGetValue(key, out kitem))
                    return kitem.Value;
                return null;
            }
            set
            {
                KeyItem kitem = null;

                if (this.TryGetValue(key, out kitem))
                {
                    kitem.Value = value;
                }
                else
                {
                    this.Add(new KeyItem(key, value));
                }
            }
        }
        #endregion

        #region ValueAs methods

        public string ValueAsString(string key, string valueIfNull = default(string))
        {
            KeyItem kitem = null;

            if (!this.TryGetValue(key, out kitem))
                return valueIfNull;

            if (string.IsNullOrEmpty(kitem.Value))
            {
                return valueIfNull;
            }
            else
                return kitem.Value;
        }

        public int ValueAsInt(string key, int valueIfNull = default(int))
        {
            return ValueAs<int>(key, valueIfNull);
        }

        public T ValueAs<T>(string key, T valueIfNull = default(T))
        {
            KeyItem kitem = null;
            Type valType = typeof(T);

            if (!this.TryGetValue(key, out kitem))
                return valueIfNull;

            if (kitem == null)
            {
                return valueIfNull;
            }

            if (valType.IsGenericType && valType.GetGenericTypeDefinition() == typeof(Nullable<>))
            {
                if (string.IsNullOrEmpty(kitem.Value))
                {
                    return valueIfNull;
                }
                else
                {
                    TypeConverter conv = TypeDescriptor.GetConverter(typeof(T));
                    return (T)conv.ConvertFrom(kitem.Value);
                }
            }
            else
            {
                if (string.IsNullOrEmpty(kitem.Value))
                {
                    return valueIfNull;
                }
            }
            return (T)Convert.ChangeType(kitem.Value, typeof(T));
        }
        #endregion
    }

}