MySql.Data.MySqlClient.MySqlException (0x80004005) — Causes and Fixes

Fix:

Check your connection string:

string connectionString = "Server=localhost;Database=mydb;User ID=root;Password=mypassword;";
using (var connection = new MySqlConnection(connectionString))
{
    connection.Open();
}

Additional steps:

• If using a remote host, ensure MySQL allows remote connections.
• Grant remote access to the MySQL user:

  GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'mypassword';
  FLUSH PRIVILEGES;

Fix:

Restart MySQL:

• Windows:
  net start mysql
• Linux:
  sudo systemctl start mysql

Fix:

Reinstall the MySql.Data NuGet package:

Install-Package MySql.Data -Version 8.0.33

Ensure you're using a compatible .NET Framework/.NET Core version.

Fix:

1. Open my.cnf (Linux) or my.ini (Windows).
2. Locate the line:

   bind-address = 127.0.0.1

3. Change it to:

   bind-address = 0.0.0.0

4. Restart MySQL.

Fix:

Check if the MySQL socket file exists:

mysql -u root -p --socket=/var/run/mysqld/mysqld.sock

If missing, restart MySQL:

sudo systemctl restart mysql

Fix:

Disable SSL in the connection string:

string connectionString = "Server=localhost;Database=mydb;User ID=root;Password=mypassword;SslMode=None;";