Search code examples
c#.netout-of-memory

C# : Out of Memory exception

Today my application threw an OutOfMemoryException. To me this was always almost impossible since I have 4GB RAM and a lot of virtual memory too. The error happened when I tried to add an existing collection to a new list.

List<Vehicle> vList = new List<Vehicle>(selectedVehicles);

To my understanding there isn't much memory allocated here since the vehicles my new list should contain already exist inside the memory. I have to admit Vehicle is a very complex class and I tried to add about 50.000 items to the new list at once. But since all Vehicles in the application come from a database that is only 200MB in size, I have no idea what may cause an OutOfMemoryException at this point.

Solution

  • Two points:

    1. If you are running a 32 bit Windows, you won't have all the 4GB accessible, only 2GB.
    2. Don't forget that the underlying implementation of List is an array. If your memory is heavily fragmented, there may not be enough contiguous space to allocate your List, even though in total you have plenty of free memory.