C#访问MySQL：连接查询

Posted 2022-05-02 LcVong

前言：
通过C#连接访问mysql：连接查询。

1.项目添加MySQL引用：

2.获取数据库一个满足条件的值：

        public static object GetSingle2(string SQLString)
        
            using (MySqlConnection connection = new MySqlConnection("host=数据库IP;Port=数据库端口;Database=数据库名;uid=数据库账户;pwd=数据库密码;Charset=utf8;Allow User Variables=true"))
            
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                
                    try
                    
                        connection.Open();
                        object obj = cmd.ExecuteScalar();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        
                            return null;
                        
                        else
                        
                            return obj;
                        
                    
                    catch (MySqlException e)
                    
                        connection.Close();
                        throw e;
                    
                
            
        

调用：

        private void Button_Click(object sender, RoutedEventArgs e)
        
            object aa =  GetSingle2(string.Format("SELECT 字段1 FROM 表名 WHERE 字段2='0'", 1));//查询表中字段2为1的数据量面字段1的值
        

3.获取数据库满足条件的表：

        public static DataSet Query(string SQLString)
        
            using (MySqlConnection connection = new MySqlConnection("host=数据库IP;Port=数据库端口;Database=数据库名;uid=数据库账户;pwd=数据库密码;Charset=utf8;Allow User Variables=true"))
            
                DataSet data = new DataSet();
                try
                
                    connection.Open();
                    MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                    command.Fill(data , "ds");
                
                catch (MySql.Data.MySqlClient.MySqlException ex)
                
                    throw new Exception(ex.Message);
                
                return ds;
            
        

调用：

        private void Button_Click(object sender, RoutedEventArgs e)
        
            DataSet data = Query(string.Format("SELECT * FROM 表名 WHERE 字段2='0'", 1));//查询表里面所有字段2为1的所有行