ASP.Net中的数据缓存

Question

I need to fill some dropdown boxex from some reference data. ie City List, Country List etc. I need to fill it in various webforms. I think, we should cache this data in our application so that, we don't hit database on every form. I am new to caching and ASP.Net. Please suggest me how to do this.

Answer 1

I always add the following class to all my projects which give me easy access to the Cache object. Implementing this, following Hasan Khan's answer would be a good way to go.

public static class CacheHelper
    {
        /// <summary>
        /// Insert value into the cache using
        /// appropriate name/value pairs
        /// </summary>
        /// <typeparam name="T">Type of cached item</typeparam>
        /// <param name="o">Item to be cached</param>
        /// <param name="key">Name of item</param>
        public static void Add<T>(T o, string key, double Timeout)
        {
            HttpContext.Current.Cache.Insert(
                key,
                o,
                null,
                DateTime.Now.AddMinutes(Timeout),
                System.Web.Caching.Cache.NoSlidingExpiration);
        }

        /// <summary>
        /// Remove item from cache
        /// </summary>
        /// <param name="key">Name of cached item</param>
        public static void Clear(string key)
        {
            HttpContext.Current.Cache.Remove(key);
        }

        /// <summary>
        /// Check for item in cache
        /// </summary>
        /// <param name="key">Name of cached item</param>
        /// <returns></returns>
        public static bool Exists(string key)
        {
            return HttpContext.Current.Cache[key] != null;
        }

        /// <summary>
        /// Retrieve cached item
        /// </summary>
        /// <typeparam name="T">Type of cached item</typeparam>
        /// <param name="key">Name of cached item</param>
        /// <param name="value">Cached value. Default(T) if item doesn't exist.</param>
        /// <returns>Cached item as type</returns>
        public static bool Get<T>(string key, out T value)
        {
            try
            {
                if (!Exists(key))
                {
                    value = default(T);
                    return false;
                }

                value = (T)HttpContext.Current.Cache[key];
            }
            catch
            {
                value = default(T);
                return false;
            }

            return true;
        }
    }

Answer 2

From other question of yours I read that you're using 3 layer architecture with dal, business and presentation layer.

So I assume that you have some data access class. Ideal thing to do would be to have a cached implementation of the same class and do caching in that.

Eg: If you have an interface IUserRepository then UserRepository class would implement it and add/delete/update entries in db via methods then you can also have CachedUserRepository which will contain instance of UserRepository object and on get methods it will first look into the cache against some key (derived from method parameters) and if the item is found then it will return it otherwise you call the method on internal object; get the data; add to cache and then return it.

Your CachedUserRepository will also have instance of cache object obviously. You can look at http://msdn.microsoft.com/en-us/library/18c1wd61(v=vs.85).aspx for details on how to use Cache object.