另一個 OracleParameterCollection 中已包含 OracleParameter

出現這個錯誤的時候，我按照百度來的方法 在finally里面加cmd.Parameters.Clear(); 在

foreach (OracleParameter parm in cmdParms)
                {
                    cmd.Parameters.Add(parm);
                }

前面加cmd.Parameters.Clear(); 都不管用 后來 發現又找到一種方法 這回管用了：

OracleParameter pp = (OracleParameter)((ICloneable)parm).Clone();
                    cmd.Parameters.Add(pp);

/// <summary>
		/// 執行查詢語句，返回DataSet
		/// </summary>
		/// <param name="SQLString">查詢語句</param>
		/// <returns>DataSet</returns>
		public static DataSet Query(string SQLString,params OracleParameter[] cmdParms)
		{
			using (OracleConnection connection = new OracleConnection(connectionString))
			{
                using (OracleCommand cmd = new OracleCommand())
                {
                    PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                    using (OracleDataAdapter da = new OracleDataAdapter(cmd))
                    {
                        DataSet ds = new DataSet();
                        try
                        {
                            da.Fill(ds, "ds");
                            cmd.Parameters.Clear();
                        }
                        catch (System.Data.OracleClient.OracleException ex)
                        {
                            throw new Exception(ex.Message);
                        }
                        finally
                        {
                            cmd.Parameters.Clear();
                        }
                        return ds;
                    }
                }
			}			
		}

private static void PrepareCommand(OracleCommand cmd,OracleConnection conn,OracleTransaction trans, string cmdText, OracleParameter[] cmdParms) 
		{
			if (conn.State != ConnectionState.Open)
				conn.Open();
			cmd.Connection = conn;
			cmd.CommandText = cmdText;
			if (trans != null)
				cmd.Transaction = trans;
			cmd.CommandType = CommandType.Text;//cmdType;
			if (cmdParms != null) 
			{
                cmd.Parameters.Clear();
                foreach (OracleParameter parm in cmdParms)
                {
                    OracleParameter pp = (OracleParameter)((ICloneable)parm).Clone();
                    cmd.Parameters.Add(pp);
                }
			}
		}