Correct way of Renting and Returning a multi-dimensional array in C# from shared ArrayPool?

Question

For example, is this the correct usage scenario?

// Rent
var rentedArray = ArrayPool<int[]>.Shared.Rent(2);

rentedArray[0] = ArrayPool<int>.Shared.Rent(10);
rentedArray[1] = ArrayPool<int>.Shared.Rent(10);

// Return
foreach (var array in rentedArray)
{
    ArrayPool<int>.Shared.Return(array, true);
}

ArrayPool<int[]>.Shared.Return(rentedArray, true);

Answer 1

Your code is correct as far as how to use the API to rent and return arrays is being used.

You rent an array with a minimum specified length using the Rent API, store it in a variable and then returning that very same array using the Return API.

Answer 2

To clarify terminology, this would commonly be called a "jagged array" or array-of-arrays.

Eg:

int[][] jaggedArray = new int[2][];
jaggedArray[0] = new int[10];
jaggedArray[1] = new int[10];

Contrast with "multi-dimensional array" as it's commonly known:

int[,] dimensionalArray = new int[2,10];

It appears the ArrayPool class only deals in single-dimensional arrays, so your jagged-array approach is probably what you want.

The code is going to be less than clear.. give some thought to whether that outer-array buffer is really necessary, for your scenario.. and, if so, how to name it in a way that is readably distinct from the inner-array buffers.