生成单据ID

      /// <summary>
      /// 生成新增的单据ID的方法
      /// </summary>
      /// <param name="TableName">表名</param>
      /// <param name="KeyName">关键字名</param>
      /// <param name="MaskSymbol">隐码字符格式，如："RK-YYYY-MM-0001","沪发(-YYYY-)-001-号"</param>
      /// <returns>返回一个新的单据的ID</returns>
      private string BuileNewID(string TableName, string KeyName, string MaskSymbol)
      {

          StringBuilder strSql = new StringBuilder();

          //SQL语句的拼接
          strSql.Append("SELECT ");
          strSql.Append(KeyName);
          strSql.Append(" FROM ");
          strSql.Append(TableName);
          strSql.Append(" ORDER BY ");
          strSql.Append(KeyName);
          strSql.Append(" DESC");

          //初始化新增组织的ID
          string NewID = "";
          string ID = "";
          string ys = "Y"; //出现y的字符
          string ms = "M"; //出现m的字符

          if (MaskSymbol.Contains("y")) //判断如果存在小写y的就返回。证明格式不正确
          {
              return null;
          }
          if (MaskSymbol.Contains("m")) //判断如果存在小写m的就返回。证明格式不正确
          {
              return null;
          }

          NewID += MaskSymbol.Substring(0, MaskSymbol.IndexOf('-'));
          int y = (MaskSymbol.Length - MaskSymbol.Replace(ys, "").Length) / ys.Length;
          int m = (MaskSymbol.Length - MaskSymbol.Replace(ms, "").Length) / ys.Length;

          string Year = System.DateTime.Now.Year.ToString();  //年份
          string Modth = System.DateTime.Now.Month.ToString(); //月份
          if (y == 4) //如果出现4个Y 格式是2010
          {
              NewID += Year;

          }
          else if (y == 2)// 如果是两位 格式是10
          {

              NewID += Year.Substring(Year.Length - 2);
          }
          if (m == 2)  //如果格式是两MM证明是有月份
          {
              if (Modth.Length == 1)
              {
                  NewID += Modth.PadLeft(2, '0');
              }
              else
              {
                  NewID += Modth;
              }
          }

          using (SqlConnection conn = new SqlConnection(SqlHelper.ConnectionString))
          {
              object obj = SqlHelper.ExecuteScalar(conn, CommandType.Text, strSql.ToString(), null);
              if (obj != null)
              {
                  ID = (string)obj;
                  NewID += ID.Substring(ID.Length - 2).ToString().PadLeft(4, '0');

              }
              else
              {
                  NewID += ID.PadLeft(3, '0') + "1";
              }
          }
          return NewID;
      }