c# - 如何使用MysqlDataReader运行多个查询

我试图在我的代码中进行如下的多个查询，但它在MySqlDataReader rdr_get_latest_build_notes = get_latest_build_notes_cmd.ExecuteReader();行抛出异常，因为我已经打开了一个rdr
我搜索了一下，发现它不受支持，我需要如何修复它的指导？

    public IEnumerable<BuildNotes_op> RetrieveBuildDetails(string BuildID)
    {
        ....
        var conn = new MySql.Data.MySqlClient.MySqlConnection();
        conn.ConnectionString = AciDev.aciDevConnectionString;
        try
        {
            Console.WriteLine("Connecting to MySQL...");
            conn.Open();
            string sql = @"query1";
            MySqlCommand cmd = new MySqlCommand(sql, conn);
            MySqlDataReader rdr = cmd.ExecuteReader(); --> **rdr open here**
            ....

            while (rdr.Read())
            {
                .....
                if (rdr[4] != DBNull.Value)
                    ....................
                else
                     ........
                     string sql_get_latest_build_notes_cmd = "query2";

                     MySqlCommand get_latest_build_notes_cmd = new MySqlCommand(sql_get_latest_build_notes_cmd, conn);
                     MySqlDataReader rdr_get_latest_build_notes = get_latest_build_notes_cmd.ExecuteReader();  --> **throws exception here**
                     if (rdr_get_latest_build_notes.HasRows)
                    {
                      ....................

                    }
                     rdr_get_latest_build_notes.Close();

                if (BuildDetails != null)
                {
                    BuildNotesDetails.Add(BuildDetails);
                }
            }
            rdr.Close();
            conn.Close();
            return BuildNotesDetails;
        }

        catch
        {
            throw;
        }
        finally
        {
            conn.Close();
        }

例外情况：

There is already an open DataReader associated with this Connection which must be closed first.

最佳答案

试试这个：

  public IEnumerable<BuildNotes_op> RetrieveBuildDetails(string BuildID)
    {

        var conn = new MySql.Data.MySqlClient.MySqlConnection();
         var conn2 = new MySql.Data.MySqlClient.MySqlConnection();
        conn.ConnectionString = AciDev.aciDevConnectionString;
        try
        {
            Console.WriteLine("Connecting to MySQL...");
            conn.Open();
            string sql = @"query1";
            MySqlCommand cmd = new MySqlCommand(sql, conn);
            MySqlDataReader rdr = cmd.ExecuteReader(); --> **rdr open here**
            ....

            while (rdr.Read())
            {
                .....
                if (rdr[4] != DBNull.Value)
                    ....................
                else
                     ........
                     string sql_get_latest_build_notes_cmd = "query2";

                     conn2.ConnectionString = AciDev.aciDevConnectionString;

                 Console.WriteLine("Connecting to MySQL...");
                  conn2.Open();
                     MySqlCommand get_latest_build_notes_cmd = new MySqlCommand(sql_get_latest_build_notes_cmd, conn2);
                     MySqlDataReader rdr_get_latest_build_notes = get_latest_build_notes_cmd.ExecuteReader();  --> **throws exception here**
                     if (rdr_get_latest_build_notes.HasRows)
                    {
                      ....................

                    }
                     rdr_get_latest_build_notes.Close();
                    conn2.Close();

                if (BuildDetails != null)
                {
                    BuildNotesDetails.Add(BuildDetails);
                }
            }
            rdr_get_latest_build_notes.Close();
            rdr.Close();
            conn.Close();
            conn2.Close();
            return BuildNotesDetails;
        }

        catch
        {
            throw;
        }
        finally
        {
            rdr_get_latest_build_notes.Close();
            rdr.Close();
            conn.Close();
            conn2.Close();
        }

创建第二个connectionvar

关于c# - 如何使用MysqlDataReader运行多个查询，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/44687408/