tbf/Results/Entities/helpers/DatabaseMigrationHelper.cs

using System;
using MySql.Data.MySqlClient;
using Common;

namespace Results.Entities.helpers
{
    public static class DatabaseMigrationHelper
    {
        public static void EnsureSchema(DBType dbType, string connectionString)
        {
            switch (dbType)
            {
                case DBType.MySql:
                    EnsureMySqlSchema(connectionString);
                    break;

                case DBType.SQLite:
                    EnsureSQLiteSchema(connectionString);
                    break;
            }
        }

        private static void EnsureMySqlSchema(string connectionString)
        {
            using (var conn = new MySqlConnection(connectionString))
            {
                conn.Open();

                EnsureColumnMySql(conn, "WaterMeterData", "Q3Channel", "INT NOT NULL DEFAULT 0");
                EnsureColumnMySql(conn, "WaterMeter",     "Q3Channel", "INT NOT NULL DEFAULT 0");
                EnsureColumnMySql(conn, "MeterTestRslt",  "Q3Channel", "INT NOT NULL DEFAULT 0");
            }
        }

        private static void EnsureColumnMySql(
            MySqlConnection conn,
            string tableName,
            string columnName,
            string columnDefinition)
        {
            using (var transaction = conn.BeginTransaction())
            {
                try
                {
                    bool exists;

                    using (var cmd = conn.CreateCommand())
                    {
                        cmd.Transaction = transaction;
                        cmd.CommandText = @"
                            SELECT COUNT(*)
                            FROM INFORMATION_SCHEMA.COLUMNS
                            WHERE TABLE_SCHEMA = DATABASE()
                              AND TABLE_NAME = @tableName
                              AND COLUMN_NAME = @columnName";

                        cmd.Parameters.AddWithValue("@tableName", tableName);
                        cmd.Parameters.AddWithValue("@columnName", columnName);

                        exists = Convert.ToInt32(cmd.ExecuteScalar()) > 0;
                    }

                    if (!exists)
                    {
                        using (var alter = conn.CreateCommand())
                        {
                            alter.Transaction = transaction;

                            alter.CommandText =
                                "ALTER TABLE `" + tableName + "` ADD COLUMN `" + columnName + "` " + columnDefinition;

                            alter.ExecuteNonQuery();
                        }
                    }

                    transaction.Commit();
                }
                catch
                {
                    transaction.Rollback();
                    throw;
                }
            }
        }

        private static void EnsureSQLiteSchema(string databaseFile)
        {
            using (var conn = new System.Data.SQLite.SQLiteConnection("Data Source=" + databaseFile))
            {
                conn.Open();

                EnsureColumnSQLite(conn, "WaterMeterData", "Q3Channel", "INTEGER NOT NULL DEFAULT 0");
                EnsureColumnSQLite(conn, "WaterMeter",     "Q3Channel", "INTEGER NOT NULL DEFAULT 0");
                EnsureColumnSQLite(conn, "MeterTestRslt",  "Q3Channel", "INTEGER NOT NULL DEFAULT 0");
            }
        }

        private static void EnsureColumnSQLite(
            System.Data.SQLite.SQLiteConnection conn,
            string tableName,
            string columnName,
            string columnDefinition)
        {
            bool exists = false;

            using (var cmd = conn.CreateCommand())
            {
                cmd.CommandText = "PRAGMA table_info(" + tableName + ")";

                using (var reader = cmd.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        if (string.Equals(reader["name"].ToString(), columnName, StringComparison.OrdinalIgnoreCase))
                        {
                            exists = true;
                            break;
                        }
                    }
                }
            }

            if (!exists)
            {
                using (var alter = conn.CreateCommand())
                {
                    alter.CommandText =
                        "ALTER TABLE " + tableName + " ADD COLUMN " + columnName + " " + columnDefinition;

                    alter.ExecuteNonQuery();
                }
            }
        }
    }
}