System out of memory exception

You've either got a memory leak somewhere (doubtful, but possible), or a handle leak. Both will give you the Out Of Memory error.

You can see if you've got a handle leak by opening TaskManager, go to View, Select Columns..., and turn on Handles. Start your process and let it run through a few iterations. Jot down the numbers you get. Then come back in a few hours and compare the numbers. If the handles numbers are considerably higher, you're not Disposing an object than you should be.

I'd consider this a definite possiblity if your process exceeds 5,000 to 8,000 handles. I've seen bad run-away processes consume over 100,000 handles (very bad!) before Windows starts to do very strange things.

It may also not be YOUR process that's causing the problem, so look at everything!

This error happens quite frequently when newbies try to do their own drawing in Windows Forms app without knowing that they have to Dispose every GDI object they create, commonly Pens and Brushes. They end up creating a new Pen or Brush on every call of their Paint event, never disposing the previous ones, and eventually they get an Out Of Memory error.

I agree withe the Answer by Estys, but you say it did not work for you -- yet. So, in addition to that:

You should not assume that a memory leak is not possible only because a garbage collection works. Many people allow the leak by holding garbage collector. Your application design is the one prone to this problem. For (one typical) example, if you improve performance of calculations by adding some intermediate values found in database to some dictionary or other container, it will hold references if you forget to clean up the container. (You may need to learn about weak references as well.)

So check up you calculation part as well.
Ask yourself: what are the variables accessed outside the loop. Check up; get rid of them as much as possible.
Also, gather some memory consumption statistics through the loop cycles.

You need to read up on memory managment in .Net, namely, about the large heap.

http://www.simple-talk.com/dotnet/.net-framework/the-dangers-of-the-large-object-heap/[^]

For more info, run this google search - ".net large heap"

Also I think a windows service would be the appropriate choice for running all the time.

C# : Out of Memory exception - Stack Overflow[^]