【DB】SQLiteHelper

    /// <summary>
    /// 说明：这是一个针对System.Data.SQLite的数据库常规操作封装的通用类。
    /// </summary>
    public class SQLiteDBHelper
    {
        private string connectionString = string.Empty;
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="dbPath">SQLite数据库文件路径</param>
        public SQLiteDBHelper(string dbPath)
        {
            this.connectionString = "Data Source=" + dbPath;
        }
        /// <summary>
        /// 创建SQLite数据库文件
        /// </summary>
        /// <param name="dbPath">要创建的SQLite数据库文件路径</param>
        public static void CreateDB(string dbPath)
        {
            using (SQLiteConnection connection = new SQLiteConnection("Data Source=" + dbPath))
            {
                    connection.Open();
                    using (SQLiteCommand command = new SQLiteCommand(connection))
                    {
                            command.CommandText = "CREATE TABLE Demo(id integer NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE)";
                            command.ExecuteNonQuery();
                            command.CommandText = "DROP TABLE Demo";
                            command.ExecuteNonQuery();
                    }
            }
        }
        /// <summary>
        /// 对SQLite数据库执行增删改操作，返回受影响的行数。
        /// </summary>
        /// <param name="sql">要执行的增删改的SQL语句</param>
        /// <param name="parameters">执行增删改语句所需要的参数，参数必须以它们在SQL语句中的顺序为准</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string sql, SQLiteParameter[] parameters)
        {
            int affectedRows = ;
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                    connection.Open();
                    using (DbTransaction transaction = connection.BeginTransaction())
                    {
                            using (SQLiteCommand command = new SQLiteCommand(connection))
                            {
                                    command.CommandText = sql;
                                    if (parameters != null)
                                    {
                                            command.Parameters.AddRange(parameters);
                                    }
                                    affectedRows = command.ExecuteNonQuery();
                            }
                            transaction.Commit();
                    }
            }
            return affectedRows;
        }
        /// <summary>
        /// 执行一个查询语句，返回一个关联的SQLiteDataReader实例
        /// </summary>
        /// <param name="sql">要执行的查询语句</param>
        /// <param name="parameters">执行SQL查询语句所需要的参数，参数必须以它们在SQL语句中的顺序为准</param>
        /// <returns></returns>
        public SQLiteDataReader ExecuteReader(string sql, SQLiteParameter[] parameters)
        {
            SQLiteConnection connection = new SQLiteConnection(connectionString);
            SQLiteCommand command = new SQLiteCommand(sql, connection);
            if (parameters != null)
            {
                    command.Parameters.AddRange(parameters);
            }
            connection.Open();
            return command.ExecuteReader(CommandBehavior.CloseConnection);
        }
        /// <summary>
        /// 执行一个查询语句，返回一个包含查询结果的DataTable
        /// </summary>
        /// <param name="sql">要执行的查询语句</param>
        /// <param name="parameters">执行SQL查询语句所需要的参数，参数必须以它们在SQL语句中的顺序为准</param>
        /// <returns></returns>
        public DataTable ExecuteDataTable(string sql, SQLiteParameter[] parameters)
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                    using (SQLiteCommand command = new SQLiteCommand(sql, connection))
                    {
                            if (parameters != null)
                            {
                                    command.Parameters.AddRange(parameters);
                            }
                            SQLiteDataAdapter adapter = new SQLiteDataAdapter(command);
                            DataTable data = new DataTable();
                            adapter.Fill(data);
                            return data;
                    }
            }
        }
        /// <summary>
        /// 执行一个查询语句，返回查询结果的第一行第一列
        /// </summary>
        /// <param name="sql">要执行的查询语句</param>
        /// <param name="parameters">执行SQL查询语句所需要的参数，参数必须以它们在SQL语句中的顺序为准</param>
        /// <returns></returns>
        public Object ExecuteScalar(string sql, SQLiteParameter[] parameters)
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                    using (SQLiteCommand command = new SQLiteCommand(sql, connection))
                    {
                            if (parameters != null)
                            {
                                    command.Parameters.AddRange(parameters);
                            }
                            SQLiteDataAdapter adapter = new SQLiteDataAdapter(command);
                            DataTable data = new DataTable();
                            adapter.Fill(data);
                            return data;
                    }
            }
        }
        /// <summary>
        /// 查询数据库中的所有数据类型信息
        /// </summary>
        /// <returns></returns>
        public DataTable GetSchema()
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                    connection.Open();
                    DataTable data=connection.GetSchema("TABLES");
                    connection.Close();
                    //foreach (DataColumn column in data.Columns)
                    //{
                    //        Console.WriteLine(column.ColumnName);
                    //}
                    return data;
            }
        }