Sqlite 操作类代码

1. ADO.NET Provider For SQLite.
　　ADO.NET 提供程序是香港(貌似)一个公司提供的.项目地址见:http://sourceforge.net/projects/sqlite-dotnet2
　　2. 对SQLite.NET的封装,提供一个简单的操作帮助类.
SQLiteHelper

代码如下：

/**//** 
* SQLite操作的帮助类. 
* 
* Author: egmkang.wang 
* Date: 2009-06-21 
*/ 
namespace System.Data.SQLite 
{ 
using System.Data; 
using System.Data.SQLite; 
using System.IO; 
public class SqliteHelper 
{ 
private static string pwd = "PWD"; 
private static string path = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase) + "\\sqliteTest.db"; 
private static string connString = string.Format("Data Source =\"{0}\"", path, pwd); 
/**//// <summary> 
/// 返回数据库链接字符串 
/// </summary> 
public static string ConnString 
{ 
get { return connString; } 
} 
/**//// <summary> 
/// 执行SQL语句,返回受影响的行数 
/// </summary> 
/// <param name="cmdText">需要被执行的SQL语句</param> 
/// <returns>受影响的行数</returns> 
public static int ExecuteNonQuery(string cmdText) 
{ 
return ExecuteNonQuery(ConnString, cmdText); 
} 
/**//// <summary> 
/// 执行带有事务的SQL语句 
/// </summary> 
/// <param name="trans">事务</param> 
/// <param name="cmdText">SQL语句</param> 
/// <returns>受影响的行数</returns> 
public static int ExecuteNonQuery(SQLiteTransaction trans, string cmdText, params SQLiteParameter[] parameters) 
{ 
int val = 0; 
using (SQLiteCommand cmd = new SQLiteCommand()) 
{ 
PrepareCommand(cmd, (SQLiteConnection)trans.Connection, trans, cmdText, parameters); 
val = cmd.ExecuteNonQuery(); 
cmd.Parameters.Clear(); 
} 
return val; 
} 
/**//// <summary> 
/// 执行SQL语句,返回受影响的行数 
/// </summary> 
/// <param name="connString">连接字符串</param> 
/// <param name="cmdText">SQL语句</param> 
/// <param name="parameters">SQL的参数</param> 
/// <returns>受影响的行数</returns> 
public static int ExecuteNonQuery(string connString, string cmdText, params SQLiteParameter[] parameters) 
{ 
using (SQLiteConnection conn = new SQLiteConnection(connString)) 
{ 
return ExecuteNonQuery(conn, cmdText, parameters); 
} 
} 
/**//// <summary> 
/// 执行SQL语句,返回受影响的行数 
/// </summary> 
/// <param name="connection">数据库链接</param> 
/// <param name="cmdText">SQL语句</param> 
/// <param name="parameters">参数</param> 
/// <returns>受影响的行数</returns> 
public static int ExecuteNonQuery(SQLiteConnection connection, string cmdText, params SQLiteParameter[] parameters) 
{ 
int val = 0; 
using (SQLiteCommand cmd = new SQLiteCommand()) 
{ 
PrepareCommand(cmd, connection, null, cmdText, parameters); 
val = cmd.ExecuteNonQuery(); 
cmd.Parameters.Clear(); 
} 
return val; 
} 
/**//// <summary> 
/// 执行查询,并返回结果集的第一行的第一列.其他所有的行和列被忽略. 
/// </summary> 
/// <param name="cmdText">SQL 语句</param> 
/// <returns>第一行的第一列的值</returns> 
public static object ExecuteScalar(string cmdText) 
{ 
return ExecuteScalar(ConnString, cmdText); 
} 
/**//// <summary> 
/// 执行查询,并返回结果集的第一行的第一列.其他所有的行和列被忽略. 
/// </summary> 
/// <param name="connString">连接字符串</param> 
/// <param name="cmdText">SQL 语句</param> 
/// <returns>第一行的第一列的值</returns> 
public static object ExecuteScalar(string connString, string cmdText) 
{ 
using (SQLiteConnection conn = new SQLiteConnection(connString)) 
{ 
return ExecuteScalar(conn, cmdText); 
} 
} 
/**//// <summary> 
/// 执行查询,并返回结果集的第一行的第一列.其他所有的行和列被忽略. 
/// </summary> 
/// <param name="connection">数据库链接</param> 
/// <param name="cmdText">SQL 语句</param> 
/// <returns>第一行的第一列的值</returns> 
public static object ExecuteScalar(SQLiteConnection connection, string cmdText) 
{ 
object val; 
using (SQLiteCommand cmd = new SQLiteCommand()) 
{ 
PrepareCommand(cmd, connection, null, cmdText); 
val = cmd.ExecuteScalar(); 
} 
return val; 
} 
/**//// <summary> 
/// 执行SQL语句,返回结果集的DataReader 
/// </summary> 
/// <param name="cmdText">SQL语句</param> 
/// <param name="parameters">参数</param> 
/// <returns>结果集的DataReader</returns> 
public static SQLiteDataReader ExecuteReader(string cmdText, params SQLiteParameter[] parameters) 
{ 
return ExecuteReader(ConnString, cmdText, parameters); 
} 
/**//// <summary> 
/// 执行SQL语句,返回结果集的DataReader 
/// </summary> 
/// <param name="connString">连接字符串</param> 
/// <param name="cmdText">SQL语句</param> 
/// <param name="parameters">参数</param> 
/// <returns>结果集的DataReader</returns> 
public static SQLiteDataReader ExecuteReader(string connString, string cmdText, params SQLiteParameter[] parameters) 
{ 
SQLiteConnection conn = new SQLiteConnection(connString); 
SQLiteCommand cmd = new SQLiteCommand(); 
try 
{ 
PrepareCommand(cmd, conn, null, cmdText, parameters); 
SQLiteDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection); 
cmd.Parameters.Clear(); 
return rdr; 
} 
catch 
{ 
conn.Close(); 
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="cmd">Command对象</param> 
/// <param name="conn">Connection对象</param> 
/// <param name="trans">Transcation对象</param> 
/// <param name="cmdText">SQL Text</param> 
/// <param name="parameters">参数实例</param> 
private static void PrepareCommand(SQLiteCommand cmd, SQLiteConnection conn, SQLiteTransaction trans, string cmdText, params SQLiteParameter[] parameters) 
{ 
if (conn.State != ConnectionState.Open) 
conn.Open(); 
cmd.Connection = conn; 
cmd.CommandText = cmdText; 
if (trans != null) 
cmd.Transaction = trans; 
if (null != parameters && parameters.Length > 0) 
{ 
cmd.Parameters.AddRange(parameters); 
} 
} 
} 
}

　　3. 增删改查:

代码如下：

Insert,Delete,Update 
const string s_AddressTreeIntoSQLite = "Insert into [AddressTree] ([Id],[ItemType],[ParentId],[Name]) values (@Id,@ItemType,@ParentId,@Name);"; 
SqliteHelper.ExecuteNonQuery(tran, s_AddressTreeIntoSQLite, 
//new SQLiteParameter[] here 
); 
Select 
const string s_AddresTreeFromSqlCE = "Select [Id],[ItemType],[ParentId],[Name] From [AddressTree];"; 
using (SqlCeDataReader rdr = SqlCeHelper.ExecuteReader(s_AddresTreeFromSqlCE )) 
{ 
while (rdr.Read()) 
{ 
//Read Data Here 
} 
}

　　4. 其他
　　SQLite性能绝对强悍.四表连接查询,查询200次,SQL CE需要44秒(with index),SQLite只需要3-6秒(with index).
插入,删除更新性能参见http://www.cnblogs.com/egmkang/archive/2009/06/06/1497678.html
　　PS:最近发现执行sql的时候,最好使用单一的长连接,而不是ConnectionString.原因很简单,嵌入式数据库没有连接池技术,
在进行数据库查询中的链接的打开关闭费用相对来说比较高昂.这一点在写程序的时候注意以下.
　　还有,有关二进制资源,需要及时释放,例如SqlCommand,这些在写Web 程序的时候体验不是很大,毕竟那种环境拥有大量
的内存,GC的效率又是比较高.