MVP Dependency Chaining Framework

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;

/************************************************************************************
*
* Copyright � 2007 Rohit Gadagkar
*
* This software is provided 'as-is', without any explicit or implied warranty. 
*
* Permission is granted to anyone to use this software for any purpose, including
* commercial applications, and to alter it and redistribute it freely, subject to the
* following restrictions:
*
* 1. The origin of this software must not be misrepresented. You must not claim that
* you wrote the original software. If you use this software in a product, 
* the following acknowledgement in the product documentation is required.
*
* "Portions Copyright � 2007 Rohit Gadagkar"
*
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
*
************************************************************************************/

namespace MVPChainingFactory.Caching.Web
{
    /// <summary>
    /// Web implementation of control store. 
    /// </summary>
    /// <typeparam name="V"></typeparam>
    public class WebControlStore<V> : IControlStore<V> 
        where V : class
        // I don't see a requirement for value types. Constraining V as class
        // lets me cast to V using dynamic cast. 
    {
        private Control _control;

        public Control Control
        {
            get { return _control; }
            set { _control = value; }
        }

        protected HttpSessionState Session
        {
            get {
                HttpContext c = HttpContext.Current;
                if (c == null) throw new
                 InvalidOperationException(@"HttpContext cannot be null. WebControlStore<V> must always be used in a web context");
                return c.Session;
            }
        }

        public WebControlStore(Control control) { Control = control; }
        private WebControlStore() { }

        #region IControlStore<V> Members

        public V this[string key]
        {
            get {
                return Session[GetCompositeKey(key)] as V;
            }
            set {
                Session[GetCompositeKey(key)] = value;
            }
        }

        #endregion

        private string GetCompositeKey(string clientKey)
        {
            if (Control == null) throw new
                InvalidOperationException(@"An instance of WebControlStore<V> must always contain a valid reference to the associated control");
            if (HttpContext.Current == null) throw new
InvalidOperationException(@"HttpContext cannot be null. WebControlStore<V> must always be used in a web context");
            return string.Format("{0}{1}{2}",
                HttpContext.Current.Request.Url.AbsolutePath,
                Control.ClientID,
                clientKey);
        }
    }
}