Heap, Stack, Boxing and Unboxing, Performance ... let's order things!

[giscus[bot]]

Heap, Stack, Boxing and Unboxing, Performance ... let's order things!

In this article I will shade some lights on some of the most used terms which seems very confusing especially for beginners: heap, stack and boxing and unboxing.
Furthermore we will also encounter internet wisdom like:
Value types get stored on the stack. Reference types on the heap
We discuss why this is wrong and what the hell performance has to do with it?

https://steven-giesel.com/blogPost/9a40d278-9a9f-49fe-bbfd-2d813a58e73e

[sabitkondakci]

Thanks for sharing, it was a nice read, well done!

I would like to add a subtle detail on "stack";

Counterintuitively stack grows downward even though we tend to visualize it - like a stack designed by arrays, last item is of the highest index or memory address - the truth is that last item put on "stack frame" will be having the lowest memory address.

Default stack size is 2MB on Windows.

public struct Model
{
     int a = 10; // memory address on stack in decimal: 2866988798
     int b = 20; // memory address on stack in decimal: 2866988794 

     // storing the reference address on stack
     ItemClass c = new ItemClass(); // memory address on stack in decimal: 2866988790
}

[linkdotnet]

Thanks @sabitkondakci for sharing. I liked that kind of information. Even though in preparation I played around the memory profiler in Rider it never come to my mind that the memory addresses are the other way around :)

[fadyfayek11]

In C# records is a value type, but when it converts to IL it's been as a class! and classes are reference types.
Can you explain it to me!

[linkdotnet]

Hey @fadyfayek11. Records itself are not value types. They are indeed reference types. Described here.

If you want to have value type records you have to use: record struct, which were introduced with C# 10.

public record struct MyDate(int Ticks);

You can check Sharplab.io how this gets translated.

More information here: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-10.0/record-structs

Bottom line: record MyRecord is translated into a class aka reference type where as record struct MyRecord will be translated into a struct aka value type.