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#?
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...
On .NET 4.5 The maximum instantiatable length of a byte array is: 2147483591, or 56 less than int.MaxValue. Found via:
for (int i = int.MaxValue; i > 0; i--)
{
try
{
byte[] b = new byte[i];
Console.Out.WriteLine("MaxValue: " + i);
Environment.Exit(0);
}
catch (Exception ignored)
{}
}
Maximum length of a byte array is: 2130702268. for example:
var countryCodes = new byte[2130702268];
I wouldn't do this in the first place. Why would you want to set all that memory aside for this in-memory database? Wouldn't you rather want either a data structure which size increments as you go along (e.g. List<int>)? Or (if preferred) use an in-memory database like sqlite?
Use Array.MaxLength:
var countryCodes = new byte[Array.MaxLength];
Pressing F12 on Array.MaxLength reveals the value:
public static int MaxLength => 0X7FFFFFC7;
which is 2,147,483,591 bytes (56 bytes less than int.MaxValue)
