What is the purpose of the row builder here?

Question

What is the purpose of the row builder here?

I just made C ++ and some C #, and I'm new to MySQL, and here I don't understand the purpose of the string constructor.

This code is part of a program that is used to extract data from a web page and paste it into an existing Word File using bookmarks.

MY CODE

using System.Collections.Generic;
using System.Configuration;
using System.Text;
using MySql.Data.MySqlClient;

namespace ARExtractionLibrary
{
    public class DataExtractor
    {
        #region Attributes
        private string _databaseConfig = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        private const int AR_TRACKER_ID = 10;
        private const int AR_NUMBER_ID = 3;
        #endregion

        #region Methods
        public Dictionary<string, Field> GetFieldData(int TicketID)
        {
            MySqlConnection sqlConnection = new MySqlConnection(_databaseConfig);
            Dictionary<string, Field> fieldsDictionary = new Dictionary<string, Field>();

            StringBuilder queryDefaultFields = new StringBuilder();
            queryDefaultFields.Append("SELECT issues.id AS TicketID, issues.subject, issues.description, ");
            queryDefaultFields.Append(" CONCAT(users.firstname,' ', users.lastname) as Author");
            queryDefaultFields.Append(" FROM issues LEFT JOIN users ON users.id =issues.author_id");
            queryDefaultFields.Append("  WHERE issues.id = @TicketID");

            StringBuilder queryCustomFields = new StringBuilder();
            queryCustomFields.Append("SELECT custom_fields.name, custom_fields.field_format, CONCAT(users.firstname,' ',users.lastname) AS value");
            queryCustomFields.Append(" FROM custom_values");
            queryCustomFields.Append(" LEFT JOIN custom_fields ON custom_values.custom_field_id = custom_fields.id");
            queryCustomFields.Append(" JOIN users ON custom_values.value = users.id");
            queryCustomFields.Append(" WHERE custom_values.customized_id = @TicketId");
            queryCustomFields.Append(" AND field_format = 'user'");
            queryCustomFields.Append(" UNION");
            queryCustomFields.Append(" SELECT custom_fields.name, custom_fields.field_format, custom_values.value");
            queryCustomFields.Append(" FROM custom_values");
            queryCustomFields.Append(" LEFT JOIN custom_fields ON custom_values.custom_field_id = custom_fields.id");
            queryCustomFields.Append(" WHERE custom_values.customized_id = @TicketId");
            queryCustomFields.Append(" AND field_format <> 'user'");

            sqlConnection.Open();

            //First query
            MySqlCommand sqlCommand = null;
            sqlCommand = new MySqlCommand(queryDefaultFields.ToString(), sqlConnection);
            sqlCommand.Parameters.AddWithValue("@TicketId", TicketID);

            MySqlDataReader sqlDataReader = sqlCommand.ExecuteReader();
            while (sqlDataReader.Read())
            {
                Field subject = new Field("Subject", sqlDataReader["subject"].ToString());
                fieldsDictionary.Add(subject.Name, subject);

                Field description = new Field("Description", sqlDataReader["description"].ToString());
                fieldsDictionary.Add(description.Name, description);

                Field ticketID = new Field("TicketID", sqlDataReader["TicketID"].ToString());
                fieldsDictionary.Add(ticketID.Name, ticketID);

                Field author = new Field("Author", sqlDataReader["Author"].ToString());
                fieldsDictionary.Add(author.Name, author);
            }
            sqlDataReader.Close();

            //Second query
            sqlCommand = new MySqlCommand(queryCustomFields.ToString(), sqlConnection);
            sqlCommand.Parameters.AddWithValue("@TicketId", TicketID);
            sqlDataReader = sqlCommand.ExecuteReader();

            while (sqlDataReader.Read())
            {
                string fieldName = sqlDataReader["name"].ToString();
                string fieldValue = sqlDataReader["value"].ToString();
                string fieldFormat = sqlDataReader["field_format"].ToString();

                if (fieldsDictionary.ContainsKey(fieldName))
                {
                    fieldsDictionary[fieldName].Values.Add(fieldValue);
                }

                else
                {
                    Field localField = new Field(fieldName, fieldValue, fieldFormat);
                    fieldsDictionary.Add(localField.Name, localField);
                }
            }
            sqlDataReader.Close();
            sqlConnection.Close();

            return fieldsDictionary;
        }

        public Dictionary<int, string> GetARs()
        {
            Dictionary<int, string> ARDictionary = new Dictionary<int, string>();
            MySqlConnection sqlConnection = new MySqlConnection(_databaseConfig);
            StringBuilder sqlCommandIsAR = new StringBuilder();
            sqlCommandIsAR.Append("SELECT issues.id AS TicketID, issues.tracker_id AS Tracker, issues.subject AS Subject, custom_values.custom_field_id, custom_values.value");
            sqlCommandIsAR.Append(" FROM issues LEFT JOIN Custom_values ON custom_values.customized_id = issues.id ");
            sqlCommandIsAR.Append(" WHERE tracker_id = @IsAR AND custom_field_id = @IsARNumber ");

            sqlConnection.Open();

            MySqlCommand commandGetARs = new MySqlCommand(sqlCommandIsAR.ToString(), sqlConnection);
            commandGetARs.Parameters.AddWithValue("@IsAR", AR_TRACKER_ID);
            commandGetARs.Parameters.AddWithValue("@IsARNumber", AR_NUMBER_ID);
            MySqlDataReader sqlDataReader = null;
            sqlDataReader = commandGetARs.ExecuteReader();

            while (sqlDataReader.Read())
            {
                string DictionaryValue = sqlDataReader["TicketID"].ToString() + " - " + sqlDataReader["Subject"].ToString();

                if (sqlDataReader["value"].ToString().Length != 0)
                {
                    DictionaryValue += " [" + sqlDataReader["value"].ToString() + "]";
                }

                int key = int.Parse(sqlDataReader["TicketID"].ToString());
                ARDictionary.Add(key, DictionaryValue);
            }

            sqlDataReader.Close();
            sqlConnection.Close();

            return ARDictionary;
        }

        #endregion
    }
}

+5

c # mysql .net

Conrad c 20 sept '12 at 12:40

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4 answers

StringBuilder , . String # , , StringBuilder , , .

, String , StringBuilder , str += "text to append" ( str String).

, , , .

+6

dcp 20 . '12 12:42

, . , string value.

, .

string s = "hello"; 
s += " world"; //NEW STRING OBJECT ALLOCATED

StringBuilder , .

StringBuilder queryDefaultFields = new StringBuilder();
queryDefaultFields.Append("hello");   //THE SAME queryDefaultFields OBJECT
queryDefaultFields.Append(" world");  //THE SAME queryDefaultFields OBJECT

+4

Tigran 20 . '12 12:42

StringBuilder (, ), , ., Append ( AppendLine), , .

0

Mitja Bonca 20 sept '12 at 12:43

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Jon · Accepted Answer · 2012-09-20T12:45:54+0000

Usually

A StringBuilderallows you to create a string without redistributing a buffer for the contents of the string in each mutation operation (the same buffer is used everywhere; it is redistributed only when the string expands beyond the current capacity). This makes the whole process of creating a large string much more productive.

In this code

; . StringBuilder ; , :

var queryDefaultFields = @"SELECT issues.id AS TicketID, issues.subject, issues.description,
                           CONCAT(users.firstname,' ', users.lastname) as Author
                           FROM issues LEFT JOIN users ON users.id =issues.author_id
                           WHERE issues.id = @TicketID";

, StringBuilder, , , " ", , .

What is the purpose of the row builder here?

Usually

In this code

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