How can I use threads to run database queries in XNA?

I'm currently developing a project with XNA that is pulling information (ID, name, file location, etc) about each of my objects (each object will be displayed on screen) from a local SQL database.

I'd like to run my database queries on a separate thread so the rendered screen doesn't freeze if the database hangs or some o开发者_StackOverflow社区ther unforeseen event occurs. I'm using XNA 4.0 and the application will only be running on windows. Is this possible, and if so, how?

There are a number of options available. Generally speaking you need the query to run in a separate thread. You can use

1. Thread pool

   • QueueUserWorkItem
   • Tasks
   • Background worker
   • Async calls to the database
   • Parallel invoke

2. Manually created threads here and here

I would start with thread pooling and see how that works, dedicated manual threads are not that robust in terms of memory management and reuse.

Not to do it at all. Seriously. There are good reasons for using threads, but your reasons are bogus:

the rendered screen doesn't freeze if the database hangs or some other unforeseen event occur

Databases dont hang and unforseen events are unforseen events. How you can cope with the database not answering for 3 minutes, for example? Show a screen with objects that are unknown?

How do you mean "best"? There are a lot of ways to use threads and they all have strengths and weaknesses.

Declaring a new thread explicitly and starting it gives you the most direct control over the execution state of that thread:

var myDbThread = new Thread(()=>myDbRepo.GetRecordById<MyEntity>(idString));
myDbThread.Start();

Now, as long as you have a reference to myDbThread, you can abort it, pause it, join on it, etc. BUT, with control comes responsibility; you have to manage the threads you create yourself.

For most parallel tasks, using the ThreadPool is recommended. However, you lose some of the control:

Action myDbLambda = () => myEntityProperty = myDbRepo.GetRecordById<MyEntity>(idString);
var asyncResult = myDbLambda.BeginInvoke();

Once asyncResult.IsComplete returns true, myEntityProperty has the value. You can also architect it as a Func, and use a callback to set the value (this is recommended). The Asynchronous Model is built in to the BeginInvoke()/EndInvoke() method pair, and many exceptions like timeouts are expected by the ThreadPool, which will simply restart the timed-out thread. However, you can't "give up" and terminate a ThreadPool thread, "joining" on a ThreadPool thread is a little trickier, and if you're launching a lot of threads, the ThreadPool will start them in 250ms intervals which may not be the best use of processor.

There are many ways to use the ThreadPool; before delegates became even more important to .NET programming in v3.5, ThreadPool.QueueUserWorkItem was the main method. Now, as I said, delegates have BeginInvoke and EndInvoke methods allowing you to kick off background processes with the asynchronous model built in behind the scenes. In WinForms/WPF, you can also create BackgroundWorker components which are event-driven, allowing you to monitor progress and completion in a GUI element.

One thing to be aware of; it is virtually never a good idea to use background threads in ASP.NET. Unless you really know what you're doing, best-case you won't get the results of the behavior you sent to the worker thread, and worst-case you can crash your site trying.