Question

I want to store a small list of a simple object (containing three strings) in my ASP.NET MVC application. The list is loaded from the database and it is updated rarely by editing some values in the site’s admin area.

I’m thinking of using HttpContext.Current.Application to store it. This way I can load it in the Global.asax:

protected void Application_Start()
{
    RegisterRoutes(RouteTable.Routes);

    HttpContext.Current.Application["myObject"] = loadDataFromSql(); // returns my object
}

And then can easily reference it from any controllers or views as needed. Then in the event, the admin area calls the updateMyObject controller action, I can just update the DB and load it in again and replace HttpContext.Current.Application["myObject"].

Are there any cons to doing this? It seems like it will work fine for what I am trying to achieve, however does anyone know of a better way to do this, assuming there is some major disadvantage to the method I’ve laid out?

Answer 1

What you actually do is Caching, and it’s great, since you reduce calls to an external storage (a database or a file, whatever). The trade-off is memory usage, of course. Now, almost any modern web framework, including ASP.NET, includes some kind of a caching mechanism. Either you use it, or you use some kind of a global variable.

Storing data in ASP.NET’s built-in Cache object has some significant advantages, since this mechanism actually checks the memory usage and removes the cached data according to some rules.

However, if the data you want to cache is intensively used across the application, and its size is not too large (say, smaller than 1 MB), you may want to store it in as a global variable.

In ASP.NET, global variables are achieved by either using the Application object, like you described in your question, or by writing public static properties/fields in an internal/public class.

Here’s my solution to static properties. Note that I use a locking object, to protect the inner data from corruption. It looks like this:

public class WhateverClass
{
  private static object theLocker = new object();
  private static YourDataType theData;
  public static YourDataType TheData
  {
    get
    {
      lock (theLocker)
      {
        return theData;
      }
    }
    set
    {
      lock (theLocker)
      {
        theData = value;
      }
    }
  }
}

The usage is very simple:

First time, in Application_Start:

protected void Application_Start()
{
    RegisterRoutes(RouteTable.Routes);

    WhateverClass.TheData = loadDataFromSql();
}

In any controller:

var myData = WhateverClass.TheData;

This approach is better because you have type safety, since this public static property can be explicitly declared with the exact type. In addition, this kind of storage is more testable since it doesn’t depend on the web context.

HTH!