C#

DateTime dt = DateTime.Now.Date;
            try
            {
                string fileLocation = "C:\\pprdate.txt";
                FileStream fs = null;
                if (!File.Exists( fileLocation ))
                {
                    using (fs = File.Create( fileLocation ))
                    {
                        fs.Close();
                        fs = null;
                    }
                }
                
                string line = null;
                TextReader readFile = new StreamReader(fileLocation);
                while (true)
                {
                    
                    line = readFile.ReadLine();
                    if (line != null)
                    {
                        DateTime sd = DateTime.Parse( line );
                        if (dt >= sd.AddDays( 16 ))
                        {
                            sd = sd.AddDays( 30 );
                            StartDate.Text = sd.ToShortDateString();
                            EndDate.Text = sd.AddDays( 30 ).ToShortDateString();
                        }
                    readFile.Close();
                    readFile = null;
                    }
                    else
                    {
                        // this is where the exception happens
                        TextWriter writeFile = new StreamWriter(fileLocation);
                        DateTime sd = dt.AddDays( 7 );
                        writeFile.WriteLine( sd );
                        StartDate.Text = sd.ToShortDateString();
                        EndDate.Text = sd.AddDays( 30 ).ToShortDateString();
                        writeFile.Close();
                        writeFile = null;
                    }
                }

Thread thr;
public delegate void Dosth();
string sth = "";
private void buttonX1_Click(object sender, EventArgs e)
        {
            thr = new Thread(Listen);
            thr.Start();   
        }
void Listen()
        {
            Soc.Bind(ipend);
            Soc.Listen(10);
            
            byte[] data = new byte[500];
            while (true)
            {
                // Accept the connection
                Socket client = Soc.Accept();
                client.Receive(data);
                sth = Encoding.ASCII.GetString(data);
                // calling the method to show the string into a textbox
                athreadedfunction();
               .
               .
               .


            }
        }
 public void writeintotext()
        {
            textBox1.Text = sth;
        }
        public void athreadedfunction()
        {
            Dosth writeinto = new Dosth(writeintotext);
            textBox1.Invoke(writeinto);
        }