Csharp/C Sharp/Thread/Threads Error

Thread code with a problem

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example14_7.cs shows code with a problem
*/
using System;
using System.Threading;
public class Example14_7 
{
  // a shared counter
  private int Runs = 0;
  // the CountUp method increments the shared counter
  public  void CountUp() 
  {
    while (Runs < 10)
    {
      int Temp = Runs;
      Temp++;
      Console.WriteLine(Thread.CurrentThread.Name + " " + Temp);
      Thread.Sleep(1000);
      Runs = Temp;
    }
  }
  public static void Main() 
  {
    // Make an instance of this class
    Example14_7 ex = new Example14_7();
    // And run the test outside of the static method
    ex.RunThreads();
  }
  public void RunThreads()
  {
    // create and launch two threads
    Thread t2 = new Thread(new ThreadStart(CountUp));
    t2.Name = "t2";
    Thread t3 = new Thread(new ThreadStart(CountUp));
    t3.Name = "t3";
    t2.Start();
    t3.Start();
  }
}