C#

using System;
using System.IO;

namespace ConsoleApplication
{
    class MainClass
    {
        public void worker()
        {
            // name of the file to be used.
            string fileName = @"c:\data.txt";

            // open the file for writing.
            StreamWriter sw = new StreamWriter(
                    new FileStream(fileName, FileMode.Create, FileAccess.Write));
            // write some contents to the file.
            sw.WriteLine("This is the first line of text");
            sw.WriteLine("and this is the second one");
            // close the file.
            sw.Close();

            // open the file for reading.
            StreamReader sr = new StreamReader(
                    new FileStream(fileName, FileMode.Open, FileAccess.Read));
            // load file contents into a string.
            string text = "";
            for (string line = sr.ReadLine(); line != null; line = sr.ReadLine())
            {
                text += line + System.Environment.NewLine;
            }
            // close the file.
            sr.Close();

            // display text and wait for user to press enter key.
            Console.WriteLine(text);
            Console.ReadLine();
        }

        [STAThread]
        static void Main(string[] args)
        {
            MainClass mc = new MainClass();
            mc.worker();
        }
    }
}

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.IO;

namespace WindowsApplication
{
    public class Form1 : System.Windows.Forms.Form
    {
        public void worker()
        {
            // name of the file to be used.
            string fileName = @"c:\data.txt";

            // open the file for writing.
            StreamWriter sw = new StreamWriter(
                    new FileStream(fileName, FileMode.Create, FileAccess.Write));
            // write some contents to the file.
            sw.WriteLine("This is the first line of text");
            sw.WriteLine("and this is the second one");
            // close the file.
            sw.Close();

            // open the file for reading.
            StreamReader sr = new StreamReader(
                    new FileStream(fileName, FileMode.Open, FileAccess.Read));
            // load file contents into a string.
            string text = "";
            for (string line = sr.ReadLine(); line != null; line = sr.ReadLine())
            {
                text += line + System.Environment.NewLine;
            }
            // close the file.
            sr.Close();

            // display text.
            textBox1.Text = text;
        }

        private System.Windows.Forms.TextBox textBox1;
        private System.ComponentModel.Container components = null;

        public Form1()
        {
            InitializeComponent();
            worker();
        }
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        private void InitializeComponent()
        {
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.SuspendLayout();
            //
            // textBox1
            //
            this.textBox1.Location = new System.Drawing.Point(8, 8);
            this.textBox1.Multiline = true;
            this.textBox1.Name = "textBox1";
            this.textBox1.ScrollBars = System.Windows.Forms.ScrollBars.Both;
            this.textBox1.Size = new System.Drawing.Size(272, 216);
            this.textBox1.TabIndex = 0;
            this.textBox1.Text = "";
            this.textBox1.WordWrap = false;
            //
            // Form1
            //
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(292, 238);
            this.Controls.Add(this.textBox1);
            this.Name = "Form1";
            this.Text = "Form";
            this.ResumeLayout(false);
        }
        #endregion

        [STAThread]
        static void Main()
        {
            Application.Run(new Form1());
        }
    }
}

#include <stdio.h>
#include <conio.h>      // provides getch()

#define FILE_NAME       "c:\\data.txt"
#define MAX_LINE_LEN    256

int main()
{
    FILE *f;                        // file handle.
    char fileName[] = FILE_NAME;    // name of the file to be used. 
    char line[MAX_LINE_LEN];        // line of text.

    // open the file for writing. 
    f = fopen(fileName, "wt");
    // write some contents to the file. 
    fprintf(f, "This is the first line of text\n"); 
    fprintf(f, "and this is the second one\n"); 
    // close the file. 
    fclose(f);

    // open the file for reading. 
    f = fopen(fileName, "rt");
    // load file contents into a string. 
    while (fgets(line, sizeof(line), f) != NULL)
    {
        printf(line);
    }
    // close the file. 
    fclose(f); 

    // wait for user to press any key. 
    getch();        // note: getch() is defined in 'conio.h'
    return 0;
}