前言
我们在开发应用是经常会需要用到一些数据的存储，存储的方式有多种，使用数据库是一种比较受大家欢迎的方式。但是对于一些小型的应用，如一些移动app，通常的数据库过于庞大，而轻便的sqlite则能解决这一问题。不但操作方便，而且只需要要一个文件即可，在这里我们来说一说使用c#语言操作sqlite数据库。
一、nuget引入sqlite库
在vs菜单：工具→nuget包管理器→管理解决方案的nuget程序包 打开nuget解决方案窗口。
搜索 sqlite，选择官方的库安装到指定的项目中。：
提示：system.data.sqlite 分为 x86 和 x64 版本，这里推荐使用nuget自动安装。使用 any cpu 编译的时候，会自动拷贝32位和64位 interop dll文件到子目录中。程序运行的时候会根据电脑的运行环境自动选择合适的dll。
二、dbhelper类库
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using system.collections.generic;using system.data;using system.data.sqlite;using system.configuration;using system.data.sqlclient;//using mysql.data.mysqlclient;namespace consoleapp5{ public class dbhelper { private readonly static string connstr = configurationmanager.connectionstrings["data source=mesclient.sqlite;version=3"].connectionstring; //获取 appsetting 设置的值 //private readonly static string appstr = configurationmanager.appsettings["testkey"]; //获取 connection 对象 public static idbconnection createconnection() { idbconnection conn = new sqliteconnection(connstr);//mysqlconnection //sqlconnection conn.open(); return conn; } //执行非查询语句 public static int executenonquery(idbconnection conn, string sql, dictionary<string, object> parameters) { using (idbcommand cmd = conn.createcommand()) { cmd.commandtext = sql; foreach (keyvaluepair<string, object> keyvaluepair in parameters) { idbdataparameter parameter = cmd.createparameter(); parameter.parametername = keyvaluepair.key; parameter.value = keyvaluepair.value; cmd.parameters.add(parameter); } return cmd.executenonquery(); } } //执行非查询语句-独立连接 public static int executenonquery(string sql, dictionary<string, object> parameters) { using (idbconnection conn = createconnection()) { return executenonquery(conn, sql, parameters); } } //查询首行首列 public static object executescalar(idbconnection conn, string sql, dictionary<string, object> parameters) { using (idbcommand cmd = conn.createcommand()) { cmd.commandtext = sql; foreach (keyvaluepair<string, object> keyvaluepair in parameters) { idbdataparameter parameter = cmd.createparameter(); parameter.parametername = keyvaluepair.key; parameter.value = keyvaluepair.value; cmd.parameters.add(parameter); } return cmd.executescalar(); } } //查询首行首列-独立连接 public static object executescalar(string sql, dictionary<string, object> parameters) { using (idbconnection conn = createconnection()) { return executescalar(conn, sql, parameters); } } //查询表 public static datatable executequery(idbconnection conn, string sql, dictionary<string, object> parameters) { datatable dt = new datatable(); using (idbcommand cmd = conn.createcommand()) { cmd.commandtext = sql; foreach (keyvaluepair<string, object> keyvaluepair in parameters) { idbdataparameter parameter = cmd.createparameter(); parameter.parametername = keyvaluepair.key; parameter.value = keyvaluepair.value; cmd.parameters.add(parameter); } using (idatareader reader = cmd.executereader()) { dt.load(reader); } } return dt; } //查询表--独立连接 public static datatable executequery(string sql, dictionary<string, object> parameters) { using (idbconnection conn = createconnection()) { return executequery(conn, sql, parameters); } } }} |
三、基本使用
1. 判断数据文件是否存在
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/// <summary>/// 检查数据库是否存在不存在创建/// </summary>/// <returns></returns>public static bool checkdatabase(){ try { //判断数据文件是否存在 bool dbexist = file.exists("mesclient.sqlite"); if (!dbexist) { sqliteconnection.createfile("mesclient.sqlite"); } return true; } catch (exception) { return false; }} |
2. 判断表是否存在
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/// <summary>/// 检查数据表是否存在，不存在创建/// </summary>/// <returns></returns>public static bool checkdatatable(string connstr){ try { using (sqliteconnection conn = new sqliteconnection(connstr)) using (sqlitecommand cmd = conn.createcommand()) { conn.open(); cmd.commandtext = "select count(*) from sqlite_master where type = 'table' and name = 'serverinfo'"; object ob = cmd.executescalar(); long tablecount = convert.toint64(ob); if (tablecount == 0) { //创建表 cmd.commandtext = @" begin; create table serverinfo (id integer primary key autoincrement,name text, url text,delaytime integer,usagecounter integer, status integer,createtime datetime); create unique index idx_serverinfo on serverinfo (name); commit; "; //此语句返回结果为0 int rowcount = cmd.executenonquery(); return true; } else if (tablecount > 1) { return false; } else { return true; } } } catch (exception ex) { return false; }} |
3. 查询
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string sql = "select * from serverinfo where name =@servername and url = @url and date(createtime)=date(@date);";dictionary<string, object> parameters = new dictionary<string, object>();parameters.add("servername",endpointelement.name);parameters.add("url", endpointelement.address);parameters.add("date", datetime.now.tostring("yyyy-mm-dd"));datatable dt=sqlitehelper.executequery(connstr, sql, parameters);if (dt.rows.count>0){ usagecounter = dt.rows[0].field<long>("usagecounter"); gettime = dt.rows[0].field<datetime>("createtime");} |
4. 新增/修改
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//存在更新，不存在插入string updatesql = "replace into serverinfo(name,url,delaytime,usagecounter, status,createtime) values(@name,@url,@delaytime,@usagecounter,@status, @createtime)";dictionary<string, object> ups = new dictionary<string, object>();ups.add("name", name);ups.add("url", url);ups.add("delaytime", delaytime);ups.add("usagecounter", usagecounter);ups.add("status", status);ups.add("createtime", datetime.now.tostring("yyyy-mm-dd hh:mm:ss"));int count= sqlitehelper.executenonquery(connstr, updatesql, ups);if (count>0){ return true;}else{ return false;} |
5. 删除
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//删除记录string updatesql = "delete from serverinfo where content=@content and flag=@flag;";dictionary<string, object> updateparameters = new dictionary<string, object>();updateparameters.add("content", content);updateparameters.add("flag", flag);int count = sqlitehelper.executenonquery(connstr, updatesql, updateparameters);if (count > 0){ return true;}else{ return false;} |
四、参考文章
- Create SQLite Database and table
- Writing to a SQLite Database in C#
- SQLite with VS2012 and .NET 4.5 — ANY CPU Build
- how to check if a table exists in C#
- SQLite auto increment issue
- Inserting a date to SQLite
- SQLite REPLACE Statement
- sqlite select with condition on date
- Using SQLite how do I index columns in a CREATE TABLE statement?
总结
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对服务器之家的支持。
原文链接：https://renqiancheng.com/2018/11/C-SQLite-数据库使用说明.html
