c#访问msyql,release下出现Unable to load DLL 'coredll',debug 正常运行

开发环境
vs2008
windows 7
mysql5.1
    
        public ArrayList GetData(string sql)
        {
            MySqlConnection conn = new MySqlConnection(_connStr);
            MySqlCommand command = null;
            MySqlDataReader reader = null;
            ArrayList retData = new ArrayList();
            try
            {
                command = conn.CreateCommand();
                command.CommandText = sql;
                conn.Open();
                reader = command.ExecuteReader();
                while (reader.Read())
                {
                    if (reader.HasRows)
                    {
                        for (int i = 0; i < reader.FieldCount; i++)
                        {
                            retData.Add(reader[i]);
                        }
                    }
                }
            }
            catch (System.Exception ex)
            {
                throw new System.Exception("data access error."+ex.Message);
            }
            conn.Close();
            conn.Dispose();
            command = null;
            reader.Close();
            reader.Dispose();
            return retData;
        }
debug 下正常,release下会出现问题
message如下:Unable to load DLL 'coredll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
StackTrace如下
  at MySql.Data.Common.Semaphore.CreateSemaphore(IntPtr securityAttributes, Int32 initialCount, Int32 maximumCount, String name)
  at MySql.Data.Common.Semaphore..ctor(Int32 initialCount, Int32 maximumCount)
  at MySql.Data.MySqlClient.MySqlPool..ctor(MySqlConnectionStringBuilder settings)
  at MySql.Data.MySqlClient.MySqlPoolManager.GetPool(MySqlConnectionStringBuilder settings)
  at MySql.Data.MySqlClient.MySqlConnection.Open()
  at BackupAndMerge.DBAcess.GetData(String sql) in C:\Users\dhan\Documents\Visual Studio 2008\Projects\BackupAndMerge\src\BackupAndMerge\DBAcess.cs:line 27