WPF C#

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" Width="240" Height="140" >
    
        Start
        
    


//File:Window.xaml.cs
using System;
using System.Windows;
using System.ComponentModel;
namespace WpfApplication1
{
    public partial class Window1 : Window
    {
        private BackgroundWorker worker = new BackgroundWorker();
        private long from= 1;
        private long to = 200;
        private long biggestPrime;
        public Window1(): base()
        {
            InitializeComponent();
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
        }
        private void Start_Click(object sender, RoutedEventArgs e)
        {
            worker.RunWorkerAsync();
            btnStart.IsEnabled = false;
            txtBiggestPrime.Text = string.Empty;
        }
        private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            btnStart.IsEnabled = true;
            txtBiggestPrime.Text = biggestPrime.ToString();
        }
        private void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            for(long current = from; current <= to; current++)
            {
                biggestPrime = current;
            }
        }
    }
}