Link office to visual studio c sharp

[Ilia Gildin]

hello
I wrote the following code to read excel data

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel; 
namespace uu
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Excel.Application xlApp;
            Excel.Workbook xlWorkBook;
            Excel.Worksheet xlWorkSheet;
            Excel.Range range;
            object misValue = System.Reflection.Missing.Value;
            int i;
            string j;
            int r;
            int c;
            xlApp = new Excel.Application();
            xlWorkBook = xlApp.Workbooks.Open("d:\\tt.xls", 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
            xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);
            range = xlWorkSheet.UsedRange;
            r = range.Rows.Count;
            c = range.Columns.Count;
            for (i = 1; i<r; i =i+1)
            {
                if ((xlWorkSheet.Cells[r, 1].Text.Equals(textBox1.Text)) && (xlWorkSheet.Cells[r, 6].Text.Equals(textBox2.Text)))
               {
                    textBox3.Text = xlWorkSheet.Cells[r, 4].Text;
                    textBox4.Text = xlWorkSheet.Cells[r, 7].Text;
                }
            }  

        }

   
        private void Form1_Load(object sender, EventArgs e)
        {
  
            
        }
    }
}

and as it gets to the loop it stuck. I did tests and it reads the my excel data table correctly
and it doesn't matter if I do == or .Equal when compare the strings.
please help