VS2019 开发 Sqlite

最新推荐文章于 2024-04-23 10:31:08 发布
原创最新推荐文章于 2024-04-23 10:31:08 发布 · 2.6k 阅读
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CC 4.0 BY-SA版权
文章标签：
#sqlite #visual studio
本文介绍如何使用C#语言和SQLite数据库进行交互，包括创建数据库、表、执行SQL语句等基本操作。文中提供了详细的代码示例，适用于初学者快速上手。
一引用sqlite库
1.1下载包
https://www.nuget.org/packages/System.Data.SQLite.Core/
复制红圈中的内容，打开VS2019中的包管理控制台
粘贴到控制台，回车即可。
成功之后在引用中可以看到
【注】一定要指定运行的平台，不然会报错。
另外可能还需要 SQLite.Interop.dll。如果报错需要把这个dll放在根目录中。可以使用everything工具搜索硬盘查看。
二使用
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 DoSqliteTest
{
    class SQLiteDB
    {
        /// <summary>
        /// 创建数据库文件
        /// </summary>
        /// <param name="fileName">文件名</param>
        public static void CreateDBFile(string fileName)
        {
            string path = Environment.CurrentDirectory + @"/Data/";
            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }
            string databaseFileName = path + fileName;
            if (!File.Exists(databaseFileName))
            {
                SQLiteConnection.CreateFile(databaseFileName);
            }
        }
        /// <summary>
        /// 删除数据库
        /// </summary>
        /// <param name="fileName">文件名</param>
        public static void DeleteDBFile(string fileName)
        {
            string path = Environment.CurrentDirectory + @"/Data/";
            if (File.Exists(path))
            {
                File.Delete(path);
            }
        }

        /// <summary>
        /// 生成连接字符串
        /// </summary>
        /// <returns></returns>
        private static string CreateConnectionString()
        {
            SQLiteConnectionStringBuilder connectionString = new SQLiteConnectionStringBuilder();
            connectionString.DataSource = @"data/dbTest.db";//此处文件名可以使用变量表示

            string conStr = connectionString.ToString();
            return conStr;
        }

        static SQLiteConnection m_dbConnection;
        /// <summary>
        /// 连接到数据库
        /// </summary>
        /// <returns></returns>
        private static SQLiteConnection dbConnection()
        {
            m_dbConnection = new SQLiteConnection(CreateConnectionString());

            m_dbConnection.Open();

            return m_dbConnection;
        }

        /// <summary>
        /// 在指定数据库中创建一个table
        /// </summary>
        /// <param name="sql">sql语言，如：create table highscores (name varchar(20), score int)</param>
        /// <returns></returns>
        public static bool CreateTable(string sql)
        {
            try
            {
                SQLiteCommand command = new SQLiteCommand(sql, dbConnection());
                command.ExecuteNonQuery();
                return true;
            }
            catch (Exception ex)
            {
                Console.WriteLine("ExecuteNonQuery(" + sql + ")Err:" + ex);
                return false;
            }
            finally
            {
                closeConn();
            }

        }

        /// <summary>
        /// 在指定数据库中删除一个table
        /// </summary>
        /// <param name="tablename">表名称</param>
        /// <returns></returns>
        public static bool DeleteTable(string tablename)
        {
            try
            {
                SQLiteCommand cmd = new SQLiteCommand("DROP TABLE IF EXISTS " + tablename, dbConnection());
                cmd.ExecuteNonQuery();
                return true;
            }
            catch (Exception ex)
            {
                Console.WriteLine("ExecuteNonQuery(DROP TABLE IF EXISTS " + tablename + ")Err:" + ex);
                return false;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 在指定表中添加列
        /// </summary>
        /// <param name="tablename">表名</param>
        /// <param name="columnname">列名</param>
        /// <param name="ctype">列的数值类型</param>
        /// <returns></returns>
        public static bool AddColumn(string tablename, string columnname, string ctype)
        {
            try
            {
                SQLiteCommand cmd = new SQLiteCommand("ALTER TABLE " + tablename + " ADD COLUMN " + columnname + " " + ctype, dbConnection());
                cmd.ExecuteNonQuery();
                return true;
            }
            catch (Exception ex)
            {
                Console.WriteLine("ExecuteNonQuery(ALTER TABLE " + tablename + " ADD COLUMN " + columnname + " " + ctype + ")Err:" + ex);
                return false;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 执行增删改查操作
        /// </summary>
        /// <param name="sql">查询语言</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string sql)
        {
            try
            {
                SQLiteCommand cmd;
                cmd = new SQLiteCommand(sql, dbConnection());
                cmd.ExecuteNonQuery().ToString();
                return 1;
            }
            catch (Exception ex)
            {
                Console.WriteLine("ExecuteNonQuery(" + sql + ")Err:" + ex);
                return 0;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 返回一条记录查询
        /// </summary>
        /// <param name="sql">sql查询语言</param>
        /// <returns>返回字符串数组</returns>
        public static string[] SqlRow(string sql)
        {
            try
            {
                SQLiteCommand sqlcmd = new SQLiteCommand(sql, dbConnection());//sql语句
                SQLiteDataReader reader = sqlcmd.ExecuteReader();
                if (!reader.Read())
                {
                    return null;
                }
                string[] Row = new string[reader.FieldCount];
                for (int i = 0; i < reader.FieldCount; i++)
                {
                    Row[i] = (reader[i].ToString());
                }
                reader.Close();
                return Row;
            }
            catch (Exception ex)
            {
                Console.WriteLine("SqlRow(" + sql + ")Err:" + ex);
                return null;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 唯一结果查询
        /// </summary>
        /// <param name="sql">sql查询语言</param>
        /// <returns>返回一个字符串</returns>
        public static string sqlone(string sql)
        {

            try
            {
                SQLiteCommand sqlcmd = new SQLiteCommand(sql, dbConnection());//sql语句
                return sqlcmd.ExecuteScalar().ToString();
            }
            catch
            {
                return "";
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 获取一列数据
        /// </summary>
        /// <param name="sql">单列查询</param>
        /// <param name="count">返回结果数量</param>
        /// <returns>返回一个数组</returns>
        public static List<string> sqlcolumn(string sql)
        {
            try
            {
                List<string> Column = new List<string>();
                SQLiteCommand sqlcmd = new SQLiteCommand(sql, dbConnection());//sql语句
                SQLiteDataReader reader = sqlcmd.ExecuteReader();
                while (reader.Read())
                {
                    Column.Add(reader[0].ToString());
                }
                reader.Close();
                return Column;
            }
            catch (Exception ex)
            {
                Console.WriteLine("sqlcolumn(" + sql + ")Err:" + ex);
                return null;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 返回记录集查询
        /// </summary>
        /// <param name="sql">sql查询语言</param>
        /// <returns>返回查询结果集</returns>
        public static DataTable SqlTable(string sql)
        {
            try
            {
                SQLiteCommand sqlcmd = new SQLiteCommand(sql, dbConnection());//sql语句
                sqlcmd.CommandTimeout = 120;
                SQLiteDataReader reader = sqlcmd.ExecuteReader();
                DataTable dt = new DataTable();
                if (reader != null)
                {
                    dt.Load(reader, LoadOption.PreserveChanges, null);
                }
                return dt;
            }
            catch (Exception ex)
            {
                Console.WriteLine("SqlReader(" + sql + ")Err:" + ex);
                return null;
            }
            finally
            {
                closeConn();
            }
        }
        /// <summary>
        /// 关闭数据库连接
        /// </summary>
        public static void closeConn()
        {
            try
            {
                if (m_dbConnection.State == ConnectionState.Open)
                    m_dbConnection.Close();
                else if (m_dbConnection.State == ConnectionState.Broken)
                {
                    m_dbConnection.Close();
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("closeConnErr:" + ex);
            }
        }

        public static void Test()
        {
            //Console.WriteLine(CreateConnectionString());
            string sql = "CREATE TABLE IF NOT EXISTS student(id integer, name varchar(20), sex varchar(2));";
            ExecuteNonQuery(sql);
        }
    }
}