Design and Architecture

aspx code:

    protected void Page_Load(object sender, EventArgs e)
    {
        // Create instance of cacheManager
        CacheManager cacheManager = new CacheManager();

        // Create instance of BC_Customer
        BC_Customer bc_Customer = new BC_Customer();

        string[] param1 = { "customers", "stephen", "lisa" };

        // Must be declared as InsertExpression degelate
        cacheManager.InsertInCache(bc_Customer.InsertCustomerName, param1);

        // Make the generic get cache item call must be declared as a QueryExpression delegate
        List<string> cNameList = (List<string>)cacheManager.GetCacheItem(bc_Customer.GetCustomerName, param1);

        DropDownList1.DataSource = cNameList;
        DropDownList1.DataBind();

        string[] param2 = { "products", "Book", "Card" };

        // Create instance of BC_Products
        BC_Products bc_Products = new BC_Products();

        // Must be declared as InsertExpression degelate
        cacheManager.InsertInCache(bc_Products.InsertProductName, param2);


        // Make the generic get cache item call must be declared as a QueryExpression delegate
        List<string> pNameList = (List<string>)cacheManager.GetCacheItem(bc_Products.GetProductName, param2);

        DropDownList2.DataSource = pNameList;
        DropDownList2.DataBind();

    }


Cache manager:


// Main delegate on which all Get requests are based on.
public delegate object QueryExpression(params object[] parameters);

// Main delegate on which all insert requests are based on.
public delegate object InsertExpression(params object[] parameters);

/// <summary>
/// Summary description for CacheManager
/// </summary>
public class CacheManager
{

    public TimeSpan CacheDuration { get; set; }
    private static object syncObject = new object();
    private bool CachingEnabled = true;

    private bool HasKey(string Key)
    {            
        return (HttpContext.Current.Cache[Key] != null);
    }

	private Object CacheItem(string sCacheKey)
    {
        return (Object)HttpRuntime.Cache[sCacheKey];
    }

    public object GetCacheItem(QueryExpression QueryExpression, params object[] param)
    {
        object objCacheItem = null;

        if (!CachingEnabled)
        {
            return objCacheItem;
        }

        if (CacheItem((string) param[0]) != null)
        {
            return CacheItem((string) param[0]);
        }
        else
        {
            lock (syncObject)
            {
                if (CacheItem((string)param[0]) != null)
                {
                    return CacheItem((string) param[0]);
                }
                else
                {
                    Object cacheItem = QueryExpression(param);

                    DateTime expiration = DateTime.Now.Add(new TimeSpan (6000));

                    HttpContext.Current.Cache.Add((string) param[0], (List<string>) cacheItem, null, expiration,
                        TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Default, null);

                    return cacheItem;
                }
            }
        }
    }

    public Object InsertInCache(InsertExpression insertExpression, params object[] param)
    {
        if (HasKey((string) param[0]))
        {
            return CacheItem((string)(param[0]));
        }


        DateTime expiration = DateTime.Now.Add(new TimeSpan (6000));

        HttpContext.Current.Cache.Add((string) param[0], insertExpression(param), null, expiration, 
                        TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Default, null);

        return CacheItem((string)(param[0]));
    }
}

// Main delegate on which all Get requests are based on.
public delegate object QueryExpression(params object[] parameters);

// Main delegate on which all insert requests are based on.
public delegate object InsertExpression(params object[] parameters);

/// <summary>
/// Summary description for CacheManager
/// </summary>
public class CacheManager
{

    public TimeSpan CacheDuration { get; set; }
    private static object syncObject = new object();
    private bool CachingEnabled = true;

    private bool HasKey(string Key)
    {            
        return ((Object)HttpRuntime.Cache[Key] != null);
    }

	private Object CacheItem(string sCacheKey)
    {
        return (Object)HttpRuntime.Cache[sCacheKey];
    }

    public object GetCacheItem(QueryExpression QueryExpression, params object[] param)
    {
        object objCacheItem = null;

        if (!CachingEnabled)
        {
            return objCacheItem;
        }

        if (CacheItem((string) param[0]) != null)
        {
            return CacheItem((string) param[0]);
        }
        else
        {
            lock (syncObject)
            {
                if (CacheItem((string)param[0]) != null)
                {
                    return CacheItem((string) param[0]);
                }
                else
                {
                    Object cacheItem = QueryExpression(param);

                    DateTime expiration = DateTime.Now.Add(new TimeSpan (6000));

                    HttpContext.Current.Cache.Add((string) param[0], (List<string>) cacheItem, null, expiration,
                        TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Default, null);

                    return cacheItem;
                }
            }
        }
    }

    public Object InsertInCache(InsertExpression insertExpression, params object[] param)
    {
        System.Web.Caching.CacheDependency cacheDependency;

        string[] dependencyKey = { (string) param[1] };

        if (HasKey((string) param[0]))
        {
            return CacheItem((string)(param[0]));
        }

        DateTime expiration = DateTime.Now.Add(new TimeSpan (6000));

        cacheDependency = new System.Web.Caching.CacheDependency(null, dependencyKey);

        HttpContext.Current.Cache.Add((string) param[0], insertExpression(param), 
            (param[1] == "" ? null : (cacheDependency)), expiration, 
                        TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Default, null);

        return CacheItem((string)(param[0]));
    }
}