PAINT.NET NOT ENOUGH MEMORY TO OPEN IMAGE 32 BIT

Internally a list uses an array, and assuming 32 bit that requires 50,000 x 4bytes = 200,000 bytes (or double that if 64 bit). In the original question the list has 50,000 items in it. Which means that the large object heap gets fragmented and in my experience this inevitably leads to out of memory errors. Why does this matter? Because the large object heap is not compacted.

NET that is over 85,000 bytes comes from the large object heap (LOH) not the normal small object heap. I know this is an old question but since none of the answers mentioned the large object heap, this might be of use to others who find this question. Note (as commented below), this is only an issue if selectedVehicles is not an ICollection. So, simplest 'Fix' if I'm right: replace List vList = new List(selectedVehicles) ДЄll the other comments and answers still apply in terms of overall design decisions - but this might be a quick fix. The simplest fix for this would be to use the List(int capacity) constructor to tell the framework what backing array size to allocate (even if you're estimating and just guessing '50000' for example), and then use the AddRange(IEnumerable collection) method to actually populate your list. The garbage collector probably won't get to those discarded arrays fast enough, and you'll get your error. If the object you are passing is is not a collection (does not implement the ICollection interface), then behind-the-scenes the List implementation is going to need to grow several (or many) times, each time leaving behind a too-small array that needs to be garbage collected.

PAINT.NET NOT ENOUGH MEMORY TO OPEN IMAGE CODE

That said, there is one other possibility that comes to mind for your code above: As you're using the 'IEnumerable' constructor to the List, you may not giving the object any hints as to the size of the collection you're passing to the List constructor. Pegram is referring to the same problem in his comment above). OutOfMemoryException (on 32-bit machines) is just as often about Fragmentation as actual hard limits on memory - you'll find lots about this, but here's my first google hit briefly discussing it.

Paint.net not enough memory to open image