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这个就比较简单了，用过sqlserver的人都知道访问数据库的时候一般都会有个SqlHelper的帮助类，这里就依葫芦画瓢写了个SqliteHelper，很简单：
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SQLite;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Thumbnail
{
public class SqliteHelper
{
string dbPath = "E:\\thumbnail.db";
string conStr = "Data Source=E:\\thumbnail.db";
static SqliteHelper _instance;
public static SqliteHelper Instance
{
get
{
if (_instance == null)
_instance = new SqliteHelper();
return _instance;
}
}
string cmdCreateTable = "CREATE TABLE IF NOT EXISTS Thumbnails (Id integer PRIMARY KEY, OrginFilePath nvarchar NOT NULL UNIQUE, ThumbnailPath nvarchar NOT NULL,LastUpdateTime datetime NOT NULL);";
string createIndex = "create index if not exists originIndex on Thumbnails (OrginFilePath)";
private SqliteHelper() { }
//如果需要初始化数据库可调用此方法
public void Init()
{
if (!File.Exists(dbPath))
{
//如果数据库文件不存在，则创建
SQLiteConnection.CreateFile(dbPath);
}
List<TransModel> models = new List<TransModel>();
models.Add(new TransModel { CmdText = cmdCreateTable });
models.Add(new TransModel { CmdText = createIndex });
bool res = ExecTransaction(models);//一个事务：如果表不存在则创建，如果索引不存在则创建
}
//执行非查询的sql语句，返回受影响的行数
public int ExecuteNonQuery(string cmdText, params SQLiteParameter[] paramters)
{
using (SQLiteConnection con = new SQLiteConnection(conStr))
{
try
{
con.Open();
using (SQLiteCommand cmd = new SQLiteCommand(con))
{
cmd.CommandText = cmdText;
if (paramters != null)
cmd.Parameters.AddRange(paramters);
return cmd.ExecuteNonQuery();
}
}
catch (SQLiteException ex)
{
//_log.E(ex);
}
return -1;
}
}
//执行非查询的sql语句，返回第一行第一列的值
public object ExecuteScalar(string cmdText, params SQLiteParameter[] parameters)
{
using (SQLiteConnection conn = new SQLiteConnection(conStr))
{
try
{
conn.Open();
using (SQLiteCommand cmd = new SQLiteCommand(conn))
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteScalar();
}
}
catch (SQLiteException ex)
{
//_log.E(ex);
}
return null;
}
}
//执行查询语句，返回查询到的结果
public DataTable GetDataTable(string cmdText, params SQLiteParameter[] parameters)
{
using (SQLiteConnection conn = new SQLiteConnection(conStr))
{
try
{
conn.Open();
using (SQLiteCommand cmd = new SQLiteCommand(conn))
{
DataTable dt = new DataTable();
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
SQLiteDataAdapter da = new SQLiteDataAdapter(cmd);
da.Fill(dt);
return dt;
}
}
catch (SQLiteException ex)
{
//_log.E(ex);
}
return null;
}
}
//执行事务，如果出现异常则回滚
public bool ExecTransaction(List<TransModel> models)
{
using (SQLiteConnection con = new SQLiteConnection(conStr))
{
try
{
con.Open();
using (SQLiteTransaction trans = con.BeginTransaction())
{
using (SQLiteCommand cmd = new SQLiteCommand(con))
{
cmd.Transaction = trans;
try
{
foreach (var model in models)
{
cmd.CommandText = model.CmdText;
if (model.Paras != null)
cmd.Parameters.AddRange(model.Paras);
cmd.ExecuteNonQuery();
}
trans.Commit();
return true;
}
catch (SQLiteException ex)
{
trans.Rollback();
//_log.E(ex);
}
}
}
}
catch (SQLiteException ex)
{
// _log.E(ex);
}
}
return false;
}
}
public class TransModel
{
public string CmdText { get; set; }
public SQLiteParameter[] Paras { get; set; }
}
}
这里有几点需要注意，所有之前的SqlConnection都换成SQLiteConnection，command也要用SQLiteCommand，即一切与SQL相关到都要改为SQLite对应的，也包括要用SQLiteParameter。最后用try-catch捕获异常时一定要catch SQLiteExcepiton这个异常，不要捕获Exception否则你拿到的异常对象就会是null。
温故而知新《ADO.NET架构》：
-
ExecuteNonQuery：执行非查询的sql语句，返回受影响的行数 -
ExecuteScalar：执行非查询的sql语句，返回第一行第一列的值 -
ExecuteReader：用来执行查询sql，按需读取（通过while循环），读取期间连接一直打开 -
DataAdapter：用来执行查询sql，一次性读取数据并加载到内存里，通过fill方法填充到DataTable里，查询量太多时可能会OOM
与ADO.NET明显的一个不同是Dapper操作数据库时不需要自己手动open（事务操作除外）。
基类
public class BaseDAL
{
public static T Execute<T>(string connectionString,Func<SQLiteConnection,T> func)
{
using(SQLiteConnection con=new SQLiteConnection(connectionString))
{
return func(con);
}
}
public static T ExecuteTransaction<T>(string connectionString,Func<SQLiteConnection,SQLiteTransaction,T> func)
{
using(var con=new SQLiteConnection(connectionString))
{
con.Open();//执行事务时才需要手动open
using(var trans=con.BeginTransaction())
{
return func(con, trans);
}
}
}
public static void ExecuteTransaction(string connectionString, Action<SQLiteConnection,SQLiteTransaction> func)
{
using (var con = new SQLiteConnection(connectionString))
{
con.Open();//执行事务时才需要手动open
using (var trans = con.BeginTransaction())
{
func(con,trans);
}
}
}
}
子类：
public class RegionDAL : BaseDAL
{
private static string conStr = ConnectString.StrFoundation;
public static List<RegionVo> Search(RegionSo so)
{
string sql = "select * from JS_REGION where 1=1";
if (so.regionCode != null)
sql += " and regionCode=@regionCode";
if (so.regionLevel != null)
sql += " and regionLevel=@regionLevel";
if (so.regionLevels != null)
sql += " and regionLevel in @regionLevels";
if (so.superiorRegionCode != null)
sql += " and superiorRegionCode=@superiorRegionCode";
var data = Execute(conStr, (con) =>
{
return con.Query<RegionVo>(sql, so).ToList();
});
return data;
}
/// <summary>
/// 同步数据（事务）
/// </summary>
/// <param name="list"></param>
/// <param name="maxVersion"></param>
/// <returns></returns>
public static void SyncData(List<RegionVo> list, long maxVersion)
{
ExecuteTransaction(conStr, (con, trans) =>
{
var putList = list.Where(o => o.operate != NJS.Entities.operateType.DELETE).ToList();
var deleteList = list.Where(o => o.operate == NJS.Entities.operateType.DELETE).ToList();
var count = con.Execute("replace into JS_REGION(namePath,regionCode,regionLevel,superiorRegionCode,superiorRegionId,id) values (@namePath,@regionCode,@regionLevel,@superiorRegionCode,@superiorRegionId,@id)", putList, trans);
count = con.Execute("delete from JS_REGION where id = @id", deleteList, trans);
count = con.Execute("update GE_SYNC_TABLE set CUR_VERSION=@version where TABLE_NAME ='JS_REGION'", new { version = maxVersion }, trans);
trans.Commit();
});
}
public static long GetSyncVersion()
{
var data = Execute<long>(conStr, con =>
{
var syncTables = con.Query<SysSyncTable>("select CUR_VERSION as curVersion from GE_SYNC_TABLE where TABLE_NAME ='JS_REGION'");
return syncTables.FirstOrDefault()?.curVersion ?? 0;
});
return data;
}
}
参考：
1. 用了Dapper之后通篇还是SqlConnection，真的看不下去了
2. 温故而知新，由ADO.NET与Dapper所联想到的
