另一个 OracleParameterCollection 中已包含 OracleParameter

出现这个错误的时候，我按照百度来的方法 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 后来 发现又找到一种方法 这回管用了：

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

/// <summary>
/// 执行查询语句，返回DataSet
/// </summary>
/// <param name="SQLString">查询语句</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);
}
}
}