請問各位高手如何把下列二維陣列
int [,,] a = new int [3,4] {1, 2, 3, 4},{5,6,7,8},{9,10,11,12}};
轉成一維陣的語法?

private void Test()
        {
            int[,] a = new int[3, 4] { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 } };
            int len1 = a.GetLength(0);
            int len2 = a.GetLength(1);
            int[] b = new int[len1 * len2];
            for (int i = 0; i < len1; i++)
            {
                for (int j = 0; j < len2; j++)
                {
                    b[i * len2 + j] = a[i, j];
                }
            }
        }