Is it possible to use a C like array in C#?

Question

I want to create a class that is basically just a fixed size array with some functions to it.
This would be done like this:

private class SomeClass : SomeSuperClass {
    private readonly SomeType[] children = new SomeType[256];
    ...
}

Now this would work logically. But I think this will make the array a seperate heap object, which I do not want.
I would much rather let it behave, as if I would be doing the following in C++:

class SomeClass : SomeSuperClass {
    SomeType children[256];
    ...
}

Is there any way of doing this in C# or do I have to rely on my compiler to know to optimize this?
It is not a big problem, but it does bother me and I could not find anything about this on my own.

Answer 1

As @EtiennedeMartel commented, you can use an inline array for this:

Inline arrays are used by the runtime team and other library authors to improve performance in your apps. Inline arrays enable a developer to create an array of fixed size in a struct type. A struct with an inline buffer should provide performance characteristics similar to an unsafe fixed size buffer.

An example in your case:

[System.Runtime.CompilerServices.InlineArray(256)]
public struct ChildrenArray
{
    private SomeType _element0;
}

private class SomeClass : SomeSuperClass {
    private readonly ChildrenArray children = new ChildrenArray();
    //...
}

children[i] will give you access to the ith element, just like with a normal array.

Note: it is available since C# 12.