无法从C＃连接到MySQL，但可以从其他应用程序连接到MySQL

Question

I wanted to change MySQL server in my C# app. The app is run in my company and both - old and new MySQL servers are only accessible from the intranet. The problem is I can connect from HeidiSQL software and from python code but not from C#...

I have tried all possible solutions what I found, for ex. disabling firewall, using different packages from NuGet, modifying connection string, I created new console project only to paste various MySQL connection code - always with same error

Message: Unable to connect to any of the specified MySQL hosts.
Source: MySql.Data
Number: 1042

I', using .net Framework 4.5.2 (4.6.1 in my test project) and MySQL Server is '5.6.44-log - MySQL Community Server (GPL)'

---

One of C# connection code example that I have tested that is NOT working

using MySql.Data.MySqlClient;
public static MySqlConnection DB_connection;

DB_connection = new MySqlConnection(@"Server=MyIP;Database=myDB;Uid=my_user;Pwd=pass;");
try
{
    DB_connection.Open();
    isConn = true;
}
catch (...)

Working python code run from the same PC

import pymysql
import pprint

connection = pymysql.connect(host='MyIP',
                             user='my_user',
                             password='pass',
                             db='myDB')

try:
    with connection.cursor() as cursor:
        sql = "select * from table;"
        cursor.execute(sql)
        # connection.commit()
        result = cursor.fetchall()
        pprint.pprint(result)
finally:
    connection.close()

Answer 1

Don't see anything wrong with your posted connection string but in case your's is a replicated scenario (I mean DB replication exists) then you will have to specify the replicated server IP/hostname as well like

Server=serverAddress1, serverAddress2, serverAddress3;Database=myDataBase;
Uid=myUsername;Pwd=myPassword;