C# SQLite数据库入门使用说明
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
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
/// <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
/// <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
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
//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
//删除记录
string updateSql =
"DELETE FROM serverinfo where content=@Content and flag=@Flag;";
Dic【原URL http://www.yidunidc.com/mggfzq.html 请说明出处】tionary<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
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