In this article I am trying to explain Custom Caching Provider in ASP.NET 4.0 or 4.5. I have created a sample in Visual Studio 2011.

Purpose

Caching enables you to store data in memory for rapid access. When the data is accessed again, applications can get the data from the cache instead of retrieving it from the original source. This can improve performance and scalability. In addition, caching makes data available when the data source is temporarily unavailable.

Code:

Step 1 : Create two new projects; one is Web Application and the other is Class Library.

Step 2: Now open the Class Library project and add a reference for System.Web assembly.

Step 3: Now inherit your class from OutputCacheProvider Class.

Step 4: Now override all Add, Get, Set and Remove Methods.

Here is sample Code.

public class FileCacheProvider : OutputCacheProvider
    {
        private string _filecachePath;

        public string FilecachePath
        {
            get
            {
                if (!string.IsNullOrEmpty(_filecachePath))
                    return _filecachePath;
                _filecachePath = System.Configuration.ConfigurationManager.AppSettings["OutputCachePath"];

                var context = HttpContext.Current;

                if (context != null)
                {
                    _filecachePath = context.Server.MapPath(_filecachePath);
                    if (!_filecachePath.EndsWith("\\"))
                        _filecachePath += "\\";
                }

                return _filecachePath;
            }
        }
        public override object Add(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Add(" + key + ", " + entry + ", " + utcExpiry + ")");

            var path = GetPathFromKey(key);

            if (File.Exists(path))
                return entry;

            using (var file = File.OpenWrite(path))
            {
                var item = new CacheItem { Expires = utcExpiry, Item = entry };
                var formatter = new BinaryFormatter();
                formatter.Serialize(file, item);
            }

            return entry;
        }
        public override object Get(string key)
        {
            Debug.WriteLine("Cache.Get(" + key + ")");
 
            var path = GetPathFromKey(key);

            if (!File.Exists(path))
                return null;

            CacheItem item = null;

            using (var file = File.OpenRead(path))
            {
                var formatter = new BinaryFormatter();
                item = (CacheItem)formatter.Deserialize(file);
            }

            if (item == null || item.Expires <= DateTime.Now.ToUniversalTime())
            {
                Remove(key);
                return null;
            }

             return item.Item;
        }
        public override void Remove(string key)
        {
            Debug.WriteLine("Cache.Remove(" + key + ")");

            var path = GetPathFromKey(key);

            if (File.Exists(path))
                File.Delete(path);
        }

        public override void Set(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Set(" + key + ", " + entry + ", " + utcExpiry + ")");

            var item = new CacheItem { Expires = utcExpiry, Item = entry };
            var path = GetPathFromKey(key);

            using (var file = File.OpenWrite(path))
            {
                var formatter = new BinaryFormatter();
                formatter.Serialize(file, item);
            }
        }
        private string GetPathFromKey(string key)
        {
            return FilecachePath + MD5(key) + ".txt";
        }

        private string MD5(string s)
        {
            var provider = new MD5CryptoServiceProvider();
            var bytes = Encoding.UTF8.GetBytes(s);
            var builder = new StringBuilder();

            bytes = provider.ComputeHash(bytes);

            foreach (var b in bytes)
                builder.Append(b.ToString("x2").ToLower());

            return builder.ToString();
        }
    }

Step 5 : Now add the class library project reference to your web application and add the following attribute to your web.config file:

  <caching>
      <outputCache defaultProvider="FileCacheProvider">
        <providers>
         <add name="FileCacheProvider" type="CustomCacheProviderLib4_5.FileCacheProvider"/>
        </providers>
      </outputCache>
    </caching>

Step 6: Now add an OutputCache Directive to your page (Default.aspx).

<%@ OutputCache VaryByParam="ID" Duration="300" %>

Step 7: Now run your web application and see that your page is loading from the Cache:



Step 8 : Here is the output window: