C#-Code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel;

//Need to add the Microsoft Office XX.X Object Library at COM

namespace ReadExcel
{
    public partial class Form1 : Form
    {
        string filePath ="";

        Excel.Application app;
        Excel.Workbook workBook;
        Excel.Worksheet workSheet;
        string[,] tableContents;

        public Form1()
        {
            InitializeComponent();

            app = new Excel.Application();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //Choose File via Dialog
            openFileDialog1.ShowDialog();
            filePath = openFileDialog1.FileName;
            textBox1.Text = filePath;

            //Read file
            workBook = app.Workbooks.Open(filePath);
            workSheet = workBook.Worksheets[1];

            //Show how many items are available
            int s=1, z = 1;
            while (workSheet.Cells[z,s].Value != null)
            {
                while (workSheet.Cells[z,s].Value != null)
                {
                    s++;

                }
                    z++;
            }
            s--;

            //Create array and write contents inside array
            tableContents = new string[s,z];
            for(int i=0;i<tableContents.GetLength(0);i++)
            {
                for(int j=0;j<tableContents.GetLength(1);j++)
                {
                    tableContents[i, j] = workSheet.Cells[j+1, i+1].Value;
                }
            }

            //Write to richtTextBox1
            richTextBox1.Clear();
            if (textBox2.Text != "" || textBox3.Text != "")
            {
                try
                {
                    richTextBox1.Text = tableContents[Convert.ToInt32(textBox2.Text)-1, Convert.ToInt32(textBox3.Text)-1];
                }
                catch(IndexOutOfRangeException ex)
                {
                    richTextBox1.Text = "Empty";
                }
                catch(Exception ex)
                {
                    richTextBox1.Text = ex.Message;
                }
            }
            else
            {
                for (int i = 0; i < tableContents.GetLength(1); i++)
                {
                    for (int j = 0; j < tableContents.GetLength(0); j++)
                    {
                        richTextBox1.Text += tableContents[j, i] + "\t";
                    }
                    richTextBox1.Text += "\n";
                }
            }
        }
    }
}