Array operations with n-dimensional array using LINQ (C#)

Question

Assume we have a jagged array

int[][] a = { new[] { 1, 2, 3, 4 }, new[] { 5, 6, 7, 8 }, new[] { 9, 10, 11, 12 } };

To get a sum of second row a

Answer 1

The 2D array doesn't have any built in way of iterating over a row or column. It's not too difficult to create your own such method though. See this class for an implementation which gets an enumerable for row and column.

public static class LINQTo2DArray
{
    public static IEnumerable Row(this T[,] Array, int Row)
    {
        for (int i = 0; i < Array.GetLength(1); i++)
        {
            yield return Array[Row, i];
        }
    }
    public static IEnumerable Column(this T[,] Array, int Column)
    {
        for (int i = 0; i < Array.GetLength(0); i++)
        {
            yield return Array[i, Column];
        }
    }
}

You can also flatten the array usinga.Cast() but you would then loose all the info about columns/rows