Performance of an array of structure types

Question

Example:

// Potentially large struct.
struct Foo
{ 
   public int A;
   public int B;
   // etc.
}

Foo[] arr = new Foo[100];

If Foo is a 100-byte structure, how many bytes will be copied to memory during the execution of the following statement:

int x = arr[0].A

That is, arr [0] is evaluated by some temporary variable (100-byte copy of the Foo instance), followed by copying .A to the variable x (4-byte copy).

Or some combination of compiler, JITer and CLR allows you to optimize this statement so that 4 bytes are Acopied directly to x.

If optimization is performed, does it persist when elements are stored in List<Foo>or when an array is passed as IList<Foo>or ArraySegment<Foo>?

Answer 1

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f.A = 123;

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Foo[] fs = new Foo[1];

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fs[0].A = 123;

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List<Foo> list = new List<Foo>();
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list[0].A = 123;

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Answer 2

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