Maximum length of byte[]?

GoHeavyOrGoHome picture GoHeavyOrGoHome · Oct 15, 2010 · Viewed 51.2k times · Source

I'm trying to create an array of bytes whose length is UInt32.MaxValue. This array is essentially a small(ish) in-memory database:

byte[] countryCodes = new byte[UInt32.MaxValue];

On my machine, however, at run-time, I get a System.OverflowException with "Arithmetic operation resulted in an overflow".

What's the deal? Do I need to use an unsafe block and malloc? How would I do that in C#?

Answer

LukeH picture LukeH · Oct 15, 2010

The current implementation of System.Array uses Int32 for all its internal counters etc, so the theoretical maximum number of elements is Int32.MaxValue.

There's also a 2GB max-size-per-object limit imposed by the Microsoft CLR.

A good discussion and workaround here...

And a few related, not-quite-duplicate, questions and answers here...