Creating database connection using a separate thread

Question

Hi I have a static class that has static variables that contain data from the database. I want these variables to be updated every 5 seconds so I created a thread, inside the same class, which will execute a function that will fetch data from the database and update the variables. But I get a nullReferenceException pointing to the line where I declare initialize my connection. Here is my code:

public static void Initialize()
    {
        if (!isInitialized)
        {
            isInitialized = true;
            Thread t = new Thread( new ThreadStart(SetProperties));
            t.Start();
        }
    }

    public static void SetProperties()
    {
        //The next line is where the NullReferenceException is pointing to
        OleDbConnection conn = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + System.Web.HttpContext.Current.Server.MapPath("cms.accdb") + "';");

        using (conn)
        { ....

Any help, please? Thanks

There is no HttpContext.Current outside of the request thread. Seriously, what you're doing is silly. You need to rethink the design a lot, ASP.NET isn't really the environment for doing something like this. — Luaan
– Luaan, Commented Apr 9, 2015 at 7:28
@Luaan Hi. Thanks for your reply. But can u please elaborate on "There is no HttpContext.Current outside of the request thread"? And why do you think what I'm doing is silly? please guide me. I'm self-learning ASP.net. — Rian
– Rian, Commented Apr 9, 2015 at 7:50
HttpContext.Current is context-sensitive. It will only have a value on the request thread, and you left that by starting a new thread (that is, your Initialize method runs on the request thread, but SetProperties doesn't). Which causes your NullReferenceException, because you're trying to access properties of a null value. Caching is one of the hardest things in computing, so you might want to learn a bit more before attempting anything serious in that regard. Multi-threading is another of the hardest things, and here you're doing both as a beginner. Bad idea :) — Luaan
– Luaan, Commented Apr 9, 2015 at 7:57

Viktor S. · Accepted Answer · 2015-04-09 08:23:41Z

1

In your new thread, you have no access to System.Web.HttpContext.Current object. You can replace

System.Web.HttpContext.Current.Server.MapPath("cms.accdb")

With

HostingEnvironment.MapPath("cms.accdb")

More info about it here: HostingEnvironment.MapPath

answered Apr 9, 2015 at 8:23

Viktor S.

12.8k1 gold badge30 silver badges56 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Rian Over a year ago

@FAngle I got an error 'The relative virtual path 'cms.accdb' is not allowed here.'. any idea?

Viktor S. Over a year ago

@Rian Check this post: stackoverflow.com/questions/6455850/…

Collectives™ on Stack Overflow

Creating database connection using a separate thread

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related