Question

I have created a custom caching provider for my MVC application. I will use this class to store/retrieve session data to an outside service (like memcached or Redis).

I would like to create the object instance once at application start so that I can reference the object from any controller, and only have to ‘new up’ the instance once. I was thinking that I would instantiate the class in the Global.asax Application_Start method. However, the instance does not seem to be accessible in any of the controllers.

What is the preferred way to instantiate and then access a (global) class in MVC?

Here is a copy of my ‘simplified’ class:

 public class PersistentSession : IPersistentSession
    {
        // prepare Dependency Injection
        public ICache cacheProvider { get; set; }

        public bool SetSessionValue(string key, string value)
        {
            return cacheProvider.PutToCache(key, value);
        }

        public bool SetSessionValue(string key, string value, TimeSpan expirationTimeSpan)
        {
            return cacheProvider.PutToCache(key, value, expirationTimeSpan);
        }

        public string FetchSessionValue(string key)
        {
            return cacheProvider.FetchFromCache(key);
        }
    }

I want to instantiate it one time so that I can access it from all controllers application wide, something like this:

 // setup PersistentSession object
 persistentSession = new PersistentSession();
 string memcachedAddress = WebConfigurationManager.AppSettings["MemcachedAddress"].ToString();
 string memcachedPort = WebConfigurationManager.AppSettings["MemcachedPort"].ToString();

 persistentSession.cacheProvider = new CacheProcessor.Memcached(memcachedAddress, memcachedPort);

Where/How in MVC should the object be instantiated to get global access from all controllers?

Answer 1

I can’t see the problem !!

all you have to do is to add (static) keyword to the definition of the methods of PersistentSession class:

public class PersistentSession : IPersistentSession
{
    // prepare Dependency Injection
    public static ICache cacheProvider { get; set; }

    public static bool SetSessionValue(string key, string value)
    {
        return cacheProvider.PutToCache(key, value);
    }

    public static bool SetSessionValue(string key, string value, TimeSpan expirationTimeSpan)
    {
        return cacheProvider.PutToCache(key, value, expirationTimeSpan);
    }

    public static string FetchSessionValue(string key)
    {
        return cacheProvider.FetchFromCache(key);
    }
}

. and you can access them using the following code from anywhere :

PersistentSession.SetSessionValue (key , value);

you can also add a static constructor to initialize any fields before accessing any member, and the constructor is called before a member of static class is accessed for the first time, so you can be sure that your class is set before being used.

public static PersistentSession ()
{
//Put your initializing code, for example:
cacheProvider = new CacheProvider();
}