Memory efficiency: Object vs struct

Object Oriented Programming is not a panacea. Procedural programming is very effective for small (and medium) sized projects.
A very rough estimation of 100000 lines of code could be assumed as the cut-off between the two programming paradigms.
:)

Previous answers absolutely miss the point.

First of all, structure vs. class does not really define executable size (there is always difference in executable size; but it depends more on how you use it; this is just the volume of the code). Generally, more volume of code makes more executable size. In particular, if you use more advanced feature, you may save executable size, not waits it, because you more depend on .NET Framework code than on the code which reside in your own executable files. For example, you can save on OOP method is your design essentially based on inheritance and late binding the way it improves the code reuse. This is how you could potentially save on classes. If you use classes just for using classes, not take deeper benefits of OOP, you may only loose some room on your disk compared to structures.

Now, your question was about saving memory. First, there is more overhead of classes compared to structures. But this is not end of story. More important (and easier to take into account) is the difference between reference types such as class instances and value types such as instances of structures. First, as reference types operate on heap, there is a little heap overhead. But reference types save stack memory, compared to value types which will make extra memory clone on stack every time the instance is passed by value; it also takes more CPU time compared to passing reference type. However, you can avoid those multiple clones by simply extensive use of by-reference function arguments. This method will gives you the most of memory economy. Also, does stack memory limit you?

Finally: this is all you have to take into account. In real life, it mostly depends on your design and on what kind of economy is more critical to your purpose. The last advice is: you cannot make your decisions unless you do some experiments.

The solution was to use procedural programming. Structs was used to group data together that belonged together.

I will write a complete article on my solution when I get the time.

Thanks for the good answers.