/// <summary>
 /// 订单助手
 /// </summary>
 class OrderIdHelper
 {
   private static readonly object Locker = new object();
   private static string _tempId = "";

   /// <summary>
   /// 生成订单编号
   /// </summary>
   public static void GenerateId()
   {
     lock (Locker)  //lock 关键字可确保当一个线程位于代码的临界区时，另一个线程不会进入该临界区。
     {
       var orderId = "Wen" + DateTime.Now.ToString("yyyyMMddHHmmss"); //年月日时分秒

       if (string.Equals(_tempId, orderId))
       {
         throw new Exception("订单号重复！");
       }

       _tempId = orderId;

       Console.WriteLine(orderId);
     }
   }
 }

 class Program
 {
   static void Main(string[] args)
   {
     //创建包含两个线程的数组
     var threads = new Thread[2]
     {
       new Thread(OrderIdHelper.GenerateId),
       new Thread(OrderIdHelper.GenerateId),
     };

     foreach (var thread in threads)
     {
       //线程启动
       thread.Start();
     }

     Console.Read();
   }
 }

/// <summary>
/// 订单助手
/// </summary>
public class OrderHelper
{
  /// <summary>
  /// 防止创建类的实例
  /// </summary>
  private OrderHelper() { }

  private static readonly object Locker = new object();
  private static int _sn = 0;

  /// <summary>
  /// 生成订单编号
  /// </summary>
  /// <returns></returns>
  public static string GenerateId()
  {
    lock (Locker)  //lock 关键字可确保当一个线程位于代码的临界区时，另一个线程不会进入该临界区。
    {
      if (_sn == int.MaxValue)
      {
        _sn = 0;
      }
      else
      {
        _sn++;
      }
      
      Thread.Sleep(100);

      return "Wen" + DateTime.Now.ToString("yyyyMMddHHmmss")+ _sn.ToString().PadLeft(10, '0');
    }
  } 
}