What is the Maximum Size that an Array can hold?

Question

In C# 2008, what is the Maximum Size that an Array can hold?

Answer 1

System.Int32.MaxValue 

Assuming you mean System.Array, ie. any normally defined array (int[], etc). This is the maximum number of values the array can hold. The size of each value is only limited by the amount of memory or virtual memory available to hold them.

This limit is enforced because System.Array uses an Int32 as it's indexer, hence only valid values for an Int32 can be used. On top of this, only positive values (ie, >= 0) may be used. This means the absolute maximum upper bound on the size of an array is the absolute maximum upper bound on values for an Int32, which is available in Int32.MaxValue and is equivalent to 2^31, or roughly 2 billion.

On a completely different note, if you're worrying about this, it's likely you're using alot of data, either correctly or incorrectly. In this case, I'd look into using a List<T> instead of an array, so that you are only using as much memory as needed. Infact, I'd recommend using a List<T> or another of the generic collection types all the time. This means that only as much memory as you are actually using will be allocated, but you can use it like you would a normal array.

The other collection of note is Dictionary<int, T> which you can use like a normal array too, but will only be populated sparsely. For instance, in the following code, only one element will be created, instead of the 1000 that an array would create:

Dictionary<int, string> foo = new Dictionary<int, string>(); foo[1000] = "Hello world!"; Console.WriteLine(foo[1000]); 

Using Dictionary also lets you control the type of the indexer, and allows you to use negative values. For the absolute maximal sized sparse array you could use a Dictionary<ulong, T>, which will provide more potential elements than you could possible think about.