MatrixHelper

using System;
using System.IO;

namespace MatrixHelp
{
    public class Matrix
    {
        public Matrix(string path)
        {
            ReadMatrixFromFile(path);
        }
        private double[][] matrix;

        public int RowsCount
        {
            get
            {
                return matrix.Length;
            }
        }
        public int ColumnsCount
        {
            get
            {
                return matrix[0].Length;
            }
        }

        public void ReadMatrixFromFile(string path)
        {
            string[] strings = File.ReadAllLines(path);
            string[][] strMatrix = Array.ConvertAll<String, String[]>(strings, s => s.Split(new char[]{' '}, StringSplitOptions.RemoveEmptyEntries));
            matrix = Array.ConvertAll<String[], Double[]>(
                    strMatrix, strArr => Array.ConvertAll<String, Double>(
                            strArr, s => Double.Parse(s)
                    )
            );
        }

        public void WriteMatrix()
        {
            int elementLength = 5;

            for (int i = 0; i < RowsCount; i++)
            {
                for (int j = 0; j < ColumnsCount; j++)
                {
                    string element = matrix[i][j].ToString();
                    if (element.Contains(","))
                        element = element.Remove(element.IndexOf(',') + 2);

                    Console.Write(new String(' ', elementLength - element.Length) + element);
                }

                Console.WriteLine();
            }

            Console.WriteLine();
        }

        public void SwapRows(int index1, int index2)
        {
            double[] row1 = matrix[index1];
            matrix[index1] = matrix[index2];
            matrix[index2] = row1;
        }

        public void AddRowTo(int targetIndex, int addingRowIndex, double multiplier)
        {
            for (int i = 0; i < ColumnsCount; i++)
            {
                matrix[targetIndex][i] += multiplier * matrix[addingRowIndex][i];
            }
        }

        public void MultiplyRow(int rowIndex, double multiplier)
        {
            for (int i = 0; i < ColumnsCount; i++)
            {
                matrix[rowIndex][i] *= multiplier;
            }
        }
    }
}

using System;

namespace MatrixHelp
{
    public class Program
    {
        public static void Main(String[] args)
        {
            var matrix = new Matrix("matrix");

            while (true)
            {
                matrix.WriteMatrix();
                switch (Console.ReadLine())
                {
                    case "s":
                    HandleSwap(matrix);
                    break;

                    case "a":
                    HandleAddRow(matrix);
                    break;

                    case "m":
                    HandleMultiplication(matrix);
                    break;

                    case "d":
                    HandleDivision(matrix);
                    break;
                }
            }
        }

        private static void HandleSwap(Matrix matrix)
        {
            Console.WriteLine("Enter two indexes:");

            string[] input = Console.ReadLine().Split(' ');
            int index1 = Int32.Parse(input[0]) - 1;
            int index2 = Int32.Parse(input[1]) - 1;

            matrix.SwapRows(index1, index2);
        }

        public static void HandleAddRow(Matrix matrix)
        {
            Console.WriteLine("Enter target row index, adding row index and multiplier:");

            string[] input = Console.ReadLine().Split(' ');
            int targetRowIndex = Int32.Parse(input[0]) - 1;
            int addingRowIndex = Int32.Parse(input[1]) - 1;
            double multiplier = Double.Parse(input[2]);

            matrix.AddRowTo(targetRowIndex, addingRowIndex, multiplier);
        }

        public static void HandleMultiplication(Matrix matrix)
        {
            Console.WriteLine("Enter row index and multiplier.");
            string[] input = Console.ReadLine().Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);
            int rowIndex = Int32.Parse(input[0]) - 1;
            double multiplier = Double.Parse(input[1]);

            matrix.MultiplyRow(rowIndex, multiplier);
        }

        public static void HandleDivision(Matrix matrix)
        {
            Console.WriteLine("Enter row index and divider.");
            string[] input = Console.ReadLine().Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);
            int rowIndex = Int32.Parse(input[0]) - 1;
            double multiplier = 1.0 / Double.Parse(input[1]);

            matrix.MultiplyRow(rowIndex, multiplier);
        }
    }
}