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;";
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，谢谢大家对小牛知识库的支持。