C# SQLite数据库入门使用说明

2019-10-29 19:58:00

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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。：

C#,SQLite,数据库

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。

C#,SQLite,数据库

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;";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