What is the difference between T[,] and T[*,*]?

arrays, c#, c#-4.0, multidimensional-array

Solution

`T[]` means a zero-based array of T (array[0] is its first element)

`T[*]` means a non-zero-based array of T (array[0] is not its first element and can even be out of bounds)

The link from your question explains that there is no array of type `T[*,*]`, because all multi-dimensional arrays of `T[,]` are treated as arrays with unknown lower-bound.

Code snippet below shows how you can create an instance of `T[*]`. Note that you can not cast it to `T[]`, because they are different types. `a[0]` here will throw an OutOfRangeException, the index of the first element in this array is 1 (ah, good old Pascal days...).

Array a = Array.CreateInstance(typeof(String), new Int32[] { 1 }, new Int32[] { 1 });
Console.WriteLine(a.GetType());    // System.String[*]  

More example code

Bonus. The C# language spec says, "The indices of the elements of an array range from 0 to Length - 1". Obviously, the language does not provide built-in support for non-zero-based arrays, it's just a custom data structure that you can create; although specific in a sense that the compiler happens to have a special symbol for its type and VS uses standard array visualizer for them when you're debugging.

See also:

How to create a 1-Dimensional Array in C# with index starting at 1

C#: Nonzero-based arrays are not CLS-compliant

Problem

Original source

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