c# Sqlite幫助類

        最近有WPF作客戶端，須要離線操做存儲數據，在項目中考慮使用Sqlite嵌入式數據庫，在網上找了很多資料，最終整理出一個公共的幫助類。

Sqlite是一個很是小巧的數據庫，基本上具有關係型數據庫操做的大多數功能，Sql語法也大同小異。下面是我整理的幫助類代碼：

1.獲取 SQLiteConnection 對象，傳入數據庫有地址便可。

   /// <summary>
        /// 得到鏈接對象
        /// </summary>
        /// <returns>SQLiteConnection</returns>
        public static SQLiteConnection GetSQLiteConnection()
        {
            //Sqlite數據庫地址
            string str = AppDomain.CurrentDomain.BaseDirectory;
            var con = new SQLiteConnection("Data Source=" + str + "DataBass\\InfoServiceDbB.db");
            return con;
        }

 2.準備操做命令參數，構造SQLiteCommand 對象：

 

/// <summary>
        /// 準備操做命令參數
        /// </summary>
        /// <param name="cmd">SQLiteCommand</param>
        /// <param name="conn">SQLiteConnection</param>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">參數數組</param>
        private static void PrepareCommand(SQLiteCommand cmd, SQLiteConnection conn, string cmdText, Dictionary<String, String> data)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Parameters.Clear();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            cmd.CommandType = CommandType.Text;
            cmd.CommandTimeout = 30;
            if (data!=null&&data.Count >= 1)
            {
                foreach (KeyValuePair<String, String> val in data)
                {
                    cmd.Parameters.AddWithValue(val.Key, val.Value);
                }
            }
        }

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3.查詢，返回DataSet

/// <summary>
        /// 查詢，返回DataSet
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">參數數組</param>
        /// <returns>DataSet</returns>
        public static DataSet ExecuteDataset(string cmdText, Dictionary<string, string> data)
        {
            var ds = new DataSet();
            using (SQLiteConnection connection = GetSQLiteConnection())
            {
                var command = new SQLiteCommand();
                PrepareCommand(command, connection, cmdText, data);
                var da = new SQLiteDataAdapter(command);
                da.Fill(ds);
            }
            return ds;
        }

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4.查詢，返回DataTable

/// <summary>
        /// 查詢，返回DataTable
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">參數數組</param>
        /// <returns>DataTable</returns>
        public static DataTable ExecuteDataTable(string cmdText, Dictionary<string, string> data)
        {
            var dt = new DataTable();
            using (SQLiteConnection connection = GetSQLiteConnection())
            {
                var command = new SQLiteCommand();
                PrepareCommand(command, connection, cmdText, data);
                SQLiteDataReader reader = command.ExecuteReader();
                dt.Load(reader);
            }
            return dt;
        }

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5.返回一行數據 DataRow

 /// <summary>
        /// 返回一行數據
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">參數數組</param>
        /// <returns>DataRow</returns>
        public static DataRow ExecuteDataRow(string cmdText, Dictionary<string, string> data)
        {
            DataSet ds = ExecuteDataset(cmdText, data);
            if (ds != null && ds.Tables.Count > 0 && ds.Tables[0].Rows.Count > 0)
                return ds.Tables[0].Rows[0];
            return null;
        }

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6.執行數據庫操做

/// <summary>
        /// 執行數據庫操做
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">傳入的參數</param>
        /// <returns>返回受影響的行數</returns>
        public static int ExecuteNonQuery(string cmdText, Dictionary<string, string> data)
        {
            using (SQLiteConnection connection = GetSQLiteConnection())
            {
                var command = new SQLiteCommand();
                PrepareCommand(command, connection, cmdText, data);
                return command.ExecuteNonQuery();
            }
        }

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7.返回SqlDataReader對象

 /// <summary>
        /// 返回SqlDataReader對象
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">傳入的參數</param>
        /// <returns>SQLiteDataReader</returns>
        public static SQLiteDataReader ExecuteReader(string cmdText, Dictionary<string, string> data)
        {
            var command = new SQLiteCommand();
            SQLiteConnection connection = GetSQLiteConnection();
            try
            {
                PrepareCommand(command, connection, cmdText, data);
                SQLiteDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection);
                return reader;
            }
            catch
            {
                connection.Close();
                command.Dispose();
                throw;
            }
        }

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8.返回結果集中的第一行第一列，忽略其餘行或列

 /// <summary>
        /// 返回結果集中的第一行第一列，忽略其餘行或列
        /// </summary>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="data">傳入的參數</param>
        /// <returns>object</returns>
        public static object ExecuteScalar(string cmdText, Dictionary<string, string> data)
        {
            using (SQLiteConnection connection = GetSQLiteConnection())
            {
                var cmd = new SQLiteCommand();
                PrepareCommand(cmd, connection, cmdText, data);
                return cmd.ExecuteScalar();
            }
        }

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9.分頁查詢

/// <summary>
        /// 分頁查詢
        /// </summary>
        /// <param name="recordCount">總記錄數</param>
        /// <param name="pageIndex">頁牽引</param>
        /// <param name="pageSize">頁大小</param>
        /// <param name="cmdText">Sql命令文本</param>
        /// <param name="countText">查詢總記錄數的Sql文本</param>
        /// <param name="data">命令參數</param>
        /// <returns>DataSet</returns>
        public static DataSet ExecutePager(ref int recordCount, int pageIndex, int pageSize, string cmdText, string countText, Dictionary<string, string> data)
        {
            if (recordCount < 0)
                recordCount = int.Parse(ExecuteScalar(countText, data).ToString());
            var ds = new DataSet();
            using (SQLiteConnection connection = GetSQLiteConnection())
            {
                var command = new SQLiteCommand();
                PrepareCommand(command, connection, cmdText, data);
                var da = new SQLiteDataAdapter(command);
                da.Fill(ds, (pageIndex - 1) * pageSize, pageSize, "result");
            }
            return ds;
        }

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10.從新組織數據庫

 當你從SQLite數據庫中刪除數據時， 未用的磁盤空間將會加入一個內部的「自由列表」中。 
 當你下次插入數據時，這部分空間能夠重用。磁盤空間不會丟失， 但也不會返還給操做系統。 
 若是刪除了大量數據，而又想縮小數據庫文件佔用的空間，執行 VACUUM 命令。 VACUUM 將會從頭從新組織數據庫
 
你能夠在你的程序中約定一個時間間隔執行一次從新組織數據庫的操做，節約空間

 public void ResetDataBass()
        {
            using (SQLiteConnection conn = GetSQLiteConnection())
            {
                var cmd = new SQLiteCommand();

                if (conn.State != ConnectionState.Open)
                    conn.Open();
                cmd.Parameters.Clear();
                cmd.Connection = conn;
                cmd.CommandText = "vacuum";
                cmd.CommandType = CommandType.Text;
                cmd.CommandTimeout = 30;
                cmd.ExecuteNonQuery();
            }
        } 

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