c#操作mysql数据库

1、下载mysql.Data.dll，在解决方案->引用中引入，并在文件头部引入

using MySql.Data.MySqlClient;

2、创建MySqlConnection对象(链接库)

string connstr = "data source=localhost;database=cs_test;user id=root;password=123456;pooling=false;charset=utf8";//pooling代表是否使用连接池
MySqlConnection conn = new MySqlConnection(connstr);

 3、创建对应操作的MySqlCommand对象（测试数据库表名characters，属性列：id，names，passwords）

string sql = "select * from characters";
MySqlCommand cmd = new MySqlCommand(sql,conn);

4、针对不同操作，MySqlCommand对象有三个常用方法

(1)查找多行 : ExecuteReader()方法

返回一个MysqlDataReader对象，包含多个行，可以用其Read方法逐行读取。

对于每行元素，可以用getXXX()方法读取属性值，XXX为该属性类型，参数为属性名或者该属性为这张表的第几列。

可以用IsDBNull()方法判断是否为空，参数只能是该属性为这张表的第几列（即只能是数字）

    conn.Open();
    MySqlDataReader reader = cmd.ExecuteReader();
    Console.WriteLine("id	姓名	密码");
    while (reader.Read())
    {
        Console.Write(reader.GetInt32("id")+"	");
        if (reader.IsDBNull(1))
        {
            Console.Write("空	");
        }
        else
        {
            Console.Write(reader.GetString("names")+"	");
        }
        if (reader.IsDBNull(2))
        {
            Console.Write("空
");
        }
        else
        {
        Console.Write(reader.GetString("passwords")+"
");
        }
    }
    conn.Close();

(2)查找单个: ExecuteScalar()

返回值为查找到的元祖第一个属性，以object类型返回

string sql2 = "select names from characters where id=2";
MySqlCommand cmd2 = new MySqlCommand(sql2,conn);
conn.Open();
string names = cmd2.ExecuteScalar().ToString();
Console.WriteLine(names);
conn.Close();

(3)增、删、改: ExecuteNonQuery()

返回值为int，不成功是0，成功是1

string sql3 = "insert into characters (names,passwords) values ('XXX','1234456')";
MySqlCommand cmd3 = new MySqlCommand(sql3,conn);
conn.Open();
int s = cmd3.ExecuteNonQuery();
if (s == 0) 
Console.WriteLine("false");
else 
Console.WriteLine("success");
conn.Close();

5、完整代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;

namespace mysql_test
{
    class mysqlcz{
        public mysqlcz()
        {
            string connstr = "data source=localhost;database=csceshi;user id=root;password=123456;pooling=false;charset=utf8";
            using (MySqlConnection conn = new MySqlConnection(connstr))
            {
                string sql = "select * from characters";
                MySqlCommand cmd = new MySqlCommand(sql,conn);
                conn.Open();
                MySqlDataReader reader = cmd.ExecuteReader();
                Console.WriteLine("id	姓名	密码");
                while (reader.Read())
                {
                    Console.Write(reader.GetInt32("id")+"	");
                    if (reader.IsDBNull(1))
                    {
                        Console.Write("空	");
                    }
                    else
                    {
                        Console.Write(reader.GetString("names")+"	");
                    }

                    if (reader.IsDBNull(2))
                    {
                        Console.Write("空
");
                    }
                    else
                    {
                        Console.Write(reader.GetString("passwords")+"
");
                    }
                }
                conn.Close();
                string sql2 = "select names from characters where id=2";
                MySqlCommand cmd2 = new MySqlCommand(sql2,conn);
                conn.Open();
                string names = cmd2.ExecuteScalar().ToString();
                Console.WriteLine(names);
                conn.Close();

                string sql3 = "insert into characters (names,passwords) values ('XXX','1234456')";
                MySqlCommand cmd3 = new MySqlCommand(sql3,conn);
                conn.Open();
                int s = cmd3.ExecuteNonQuery();
                if (s == 0) Console.WriteLine("false");
                else Console.WriteLine("success");
                conn.Close();
            }
            Console.ReadLine();
        }        
        
       
    }
    class Program
    {
        static void Main(string[] args)
        {
            mysqlcz mt = new mysqlcz();
        }
    }
}

 6、sql语句参数化

为防止sql注入，尽量不要使用字符串拼接的方法拼接sql字符串

string uname=Console.ReadLine();
string upwd=Console.ReadLine();//获取用户输入
string sql="insert into characters (names,passwords) values (@name,@pwd)";//使用@符构造sql变量
MysqlCommand cmd = new MysqlCommand(sql,conn);
//使用MysqlCommand对象的parameters属性，该属性为像sql语句传递的参数集合，使用add方法向其中添加参数，参数以MysqlParameters对象形式传递
cmd.parameters.Add(new MysqlParametes("@name",uname));
cmd.parameters.Add(new MysqlParameters("@pwd",upwd));
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();