sqlite操作类

    public abstract class SQLiteHelper
    {
        public static string connectionString = System.Web.HttpContext.Current.Server.MapPath("~/DOWhat.s3db");

        #region 准备一个命令
        /// <summary>
        ///
        /// </summary>
        /// <param name="cmd">SQLiteCommand</param>
        /// <param name="conn">数据库连接字符串</param>
        /// <param name="trans">事务</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="cmdParms">sql参数</param>
        private static void PrepareCommand(SQLiteCommand cmd,SQLiteConnection conn,SQLiteTransaction trans, string cmdText,SQLiteParameter[] cmdParms)
        {

            if (conn.State != ConnectionState.Open)
            {
                SQLiteConnectionStringBuilder connsb = new SQLiteConnectionStringBuilder();
                connsb.DataSource = connectionString;
                conn.ConnectionString = connsb.ToString();
                conn.Open();
            }
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            if (trans != null)
            {
                cmd.Transaction = trans;
            }  
            cmd.CommandType = CommandType.Text;//cmdType;
            if (cmdParms != null)
            {
                foreach (SQLiteParameter parameter in cmdParms)
                {
                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&
                        (parameter.Value == null))
                    {
                        parameter.Value = DBNull.Value;
                    }
                    cmd.Parameters.Add(parameter);
                }
            }
        }
        #endregion

        #region 执行一条计算查询结果语句，返回查询结果
        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString)
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                using (SQLiteCommand cmd = new SQLiteCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, null);
                        object obj = cmd.ExecuteScalar();
                        cmd.Parameters.Clear();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (System.Data.SQLite.SQLiteException e)
                    {
                        throw e;
                    }
                }
            }
        }

        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString, params SQLiteParameter[] cmdParms)
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                using (SQLiteCommand cmd = new SQLiteCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                        object obj = cmd.ExecuteScalar();
                        cmd.Parameters.Clear();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (System.Data.SQLite.SQLiteException e)
                    {
                        throw e;
                    }
                }
            }
        }
        #endregion

        #region 执行一条SQL selet update delete返回是否成功的结果
        /// <summary>
        /// 执行一条SQL selet update delete返回是否成功的结果
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <returns>操作是否成功（bool）</returns>
        public static bool SQLExecute(string SQLString)
        {
            using (SQLiteConnection connection = new SQLiteConnection(connectionString))
            {
                using (SQLiteCommand cmd = new SQLiteCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, null);
                        int i = cmd.ExecuteNonQuery();
                        cmd.Parameters.Clear();
                        if (1==i)
                        {
                            return true;
                        }
                        else
                        {
                            return false;
                        }
                    }
                    catch (System.Data.SQLite.SQLiteException e)
                    {
                        throw e;
                    }
                }
            }
        }
        #endregion

        #region 返回一个数据集
        public static DataSet GetDS(string SQL)
        {
            using (SQLiteConnection connection =new SQLiteConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    SQLiteDataAdapter cmd = new SQLiteDataAdapter(SQL, connection);
                    cmd.Fill(ds, "ds");
                }
                catch (System.Data.SQLite.SQLiteException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }

        #endregion

    }