using System;

​

public class Program

{

    public static void Main()

    {

        int[, ] A = new int[, ]{{1, 2, 3}, {4, 5, 6}};

        System.Console.WriteLine("A = ");

        Print2DMatrix(A);

        System.Console.WriteLine();

        int[, ] B = new int[, ]{{7, 8}, {8, 9}, {9, 0}};

        System.Console.WriteLine("B = ");

        Print2DMatrix(B);

        System.Console.WriteLine();

        int[, ] C = Multiply(A, B);

        System.Console.WriteLine("A x B = ");

        Print2DMatrix(C);

    }

​

    public static int[, ] Multiply(int[, ] A, int[, ] B)

    {

        if (A.GetLength(1) != B.GetLength(0))

        {

            throw new NotSupportedException("Columns of A and Rows of B must be equal.");

        }

​

        int[, ] result = new int[A.GetLength(0), B.GetLength(1)];

        Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", "i", "j", "k", "A[i,k]", "B[k,j]", "C[i,j]");

        Console.WriteLine(new string ('=', 3 * 4 + 3 * 6 + 5 * 3));

        for (int i = 0; i < A.GetLength(0); i++)

        {

            Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", i, "", "", "", "", "");

            for (int j = 0; j < B.GetLength(1); j++)

            {

                Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", "", j, "", "", "", "");

                result[i, j] = 0;

                Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", "", "", "", "", "", result[i, j]);

                for (int k = 0; k < A.GetLength(1); k++)

                {

                    Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", "", "", k, A[i, k], B[k, j], "");

                    result[i, j] += A[i, k] * B[k, j];

                    Console.WriteLine("{0,4} | {1,4} | {2,4} | {3,6} | {4,6} | {5,6}", "", "", "", "", "", result[i, j]);

                }

            }

        }

​

        return result;

    }

​

    public static void Print2DMatrix(int[, ] M)

    {

        for (int i = 0; i <= M.GetUpperBound(0); i++)

        {

            for (int j = 0; j <= M.GetUpperBound(1); j++)

            {

                Console.Write("{0,6}", M[i, j]);

            }

​

            Console.WriteLine();

        }

    }

}