SQLite访问封装类(转)

  SQLite作为windows mobile的数据库，是一种不错的选择。SQLite的下载地址为：SQLite，SQLite的ADO.net Provider下载地址为：System.Data.SQLite ，在发布程序时，请别忘记拷贝SQLite.Interop.065.DLL、system.data.sqlite.dll两个文件到安装目录下。
    本文非原创，而是参考egmkang撰写的 WM下访问SQLite(一种替代SQL CE的解决方案)  ,并根据我自己的编程需要和习惯做了少许修改，错误在所难免。下面实现的是一个SQLiteHelper封装类:

using System.Data;
using System.Data.SQLite;
using System.IO;

namespace MyHelper.DataAccess
{
    public class SQLiteHelper
    {
        private static string password = "***";  //请修改***为实际密码
        private static string dbFilePath = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly()
            .GetName().CodeBase) + "\\***.db";  //请修改***为实际SQLite数据库名
        private static string connectString = string.Format("Data Source =\"{0}\"", dbFilePath, password);
        private static SQLiteConnection myConnect = new SQLiteConnection(connectString);

        /**//// <summary>
        /// 取当前SQLite连接
        /// </summary>
        /// <returns>当前SQLite连接</returns>
        public static SQLiteConnection GetConnection()
        {
            return myConnect;
        }

        /**//// <summary>
        /// 执行SQL语句,返回受影响的行数
        /// </summary>
        /// <param name="commandString">SQL语句</param>
        /// <param name="parameters">SQL语句参数</param>
        /// <returns>受影响的行数</returns>
        public static int ExecuteNonQuery(string commandString, params SQLiteParameter[] parameters)
        {
            int result = 0;
            using (SQLiteCommand command = new SQLiteCommand())
            {
                PrepareCommand(command, null, commandString, parameters);
                result = command.ExecuteNonQuery();
                command.Parameters.Clear();
            }
            return result;
        }

        /**//// <summary>
        /// 执行带事务的SQL语句,返回受影响的行数
        /// </summary>
        /// <param name="transaction">SQL事务</param>
        /// <param name="commandString">SQL语句</param>
        /// <param name="parameters">SQL语句参数</param>
        /// <returns>受影响的行数</returns>
        public static int ExecuteNonQuery(SQLiteTransaction transaction, string commandString,
            params SQLiteParameter[] parameters)
        {
            int result = 0;
            using (SQLiteCommand command = new SQLiteCommand())
            {
                PrepareCommand(command, transaction, commandString, parameters);
                result = command.ExecuteNonQuery();
                command.Parameters.Clear();
            }
            return result;
        }

        /**//// <summary>
        /// 执行查询,并返回结果集的第一行第一列的值,忽略其它所有的行和列
        /// </summary>
        /// <param name="commandString">SQL语句</param>
        /// <param name="parameters">SQL语句参数</param>
        /// <returns>第一行第一列的值</returns>
        public static object ExecuteScalar(string commandString, params SQLiteParameter[] parameters)
        {
            object result;
            using (SQLiteCommand command = new SQLiteCommand())
            {
                PrepareCommand(command, null, commandString, parameters);
                result = command.ExecuteScalar();
            }
            return result;
        }

        /**//// <summary>
        /// 执行SQL语句,返回结果集的DataReader
        /// </summary>
        /// <param name="commandString">SQL语句</param>
        /// <param name="parameters">SQL语句参数</param>
        /// <returns>结果集的DataReader</returns>
        public static SQLiteDataReader ExecuteReader(string commandString, params SQLiteParameter[] parameters)
        {
            SQLiteCommand command = new SQLiteCommand();
            try
            {
                PrepareCommand(command, null, commandString, parameters);
                SQLiteDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection);
                command.Parameters.Clear();
                return reader;
            }
            catch
            {
                throw;
            }
        }

        /**//// <summary>
        /// 预处理Command对象,数据库链接,事务,需要执行的对象,参数等的初始化
        /// </summary>
        /// <param name="command">Command对象</param>
        /// <param name="transaction">transaction对象</param>
        /// <param name="commandString">SQL语句</param>
        /// <param name="parameters">SQL语句参数</param>
        private static void PrepareCommand(SQLiteCommand command, SQLiteTransaction transaction,
            string commandString, params SQLiteParameter[] parameters)
        {
            if (myConnect.State != ConnectionState.Open)
                myConnect.Open();

            command.Connection = myConnect;
            command.CommandText = commandString;

            if (transaction != null)
                command.Transaction = transaction;
            if (parameters != null && parameters.Length > 0)
            {
                command.Parameters.AddRange(parameters);
            }
        }
    }
}

    为了提高效率，我将数据库连接修改为长连接。这样，只有第一次连接时会比较耗时，以后的操作就比较快了。如果本文有错误的地方，请大家参考egmkang原文。