C#

column = new DataColumn();
column.DataType = Type.GetType("System.Double");
column.ColumnName = "Total";
ds.Tables[0].Columns.Add(column);
ds.Tables[0].Columns["Total"].Expression = "UnitPrice * Quantity";

string attributeWindowsLogin = ConfigurationManager.AppSettings["WindowsLogin"].ToString();
            string attributeFullName = ConfigurationManager.AppSettings["FullName"].ToString();
            string attributeAlpSid = ConfigurationManager.AppSettings["ALPSID"].ToString();

const string dataFile = @"D:\\test.txt";
        string line;
        public Form1()
        {
            InitializeComponent();
            InitializeBackgroundWorker();
        }

        private void InitializeBackgroundWorker()
        {
            backgroundWorker1.DoWork +=
                new DoWorkEventHandler(backgroundWorker1_DoWork);
            backgroundWorker1.RunWorkerCompleted +=
                new RunWorkerCompletedEventHandler(
            backgroundWorker1_RunWorkerCompleted);
            backgroundWorker1.ProgressChanged +=
                new ProgressChangedEventHandler(
            backgroundWorker1_ProgressChanged_1);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            
            backgroundWorker1.RunWorkerAsync();//300 gives a total of 3 seconds pause
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            StringBuilder sb = new StringBuilder();
            
            using (FileStream fs = File.Open(dataFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            using (BufferedStream bs = new BufferedStream(fs))
            using (StreamReader sr = new StreamReader(bs))
            {

                while ((line = sr.ReadLine()) != null)//Exception of type 'System.OutOfMemoryException' was thrown."
                {
                    if (backgroundWorker1.CancellationPending)//checks for cancel request
                    {
                        e.Cancel = true;
                        break;
                    }

                    
                    sb.AppendLine(line + "\n");
                    e.Result = sb;

                }
            }
                
	           
        }

        

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
	        {
	            if (e.Cancelled)//it doesn't matter if the BG worker ends normally, or gets cancelled,
	            {              //both cases RunWorkerCompleted is invoked, so we need to check what has happened
	                MessageBox.Show("You've cancelled the backgroundworker!");
	 
	            }
	            else
	            {
	               
                    richTextBox1.AppendText(e.Result.ToString());
	                MessageBox.Show("Done");
                   
	            }
	        }
        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
	        {
	            progressBar1.Value = e.ProgressPercentage;
	        }

        private void backgroundWorker1_ProgressChanged_1(object sender, ProgressChangedEventArgs e)
        {
            //progressBar1.Value = e.ProgressPercentage;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            backgroundWorker1.CancelAsync();//makes the backgroundworker stop
        }