Connect to a MySql In App database in Azure successfully

Sunday, April 17, 2022

TL;DR: The default connection string provided by Azure MySQL In App is unusable from .NET. Save yourself some time and convert it before use.

New discovery: the port number for the MySQL-instance for your app may change at any moment when the App Service is upgraded or moved. So make sure you parse the environment variable MYSQLCONNSTR_localdb to obtain the current port number. I'm assuming the user name and password don't change, but maybe you shouldn't assume that, either.

For a while now, Azure supports "MySQL in App" for App Services. In a nutshell, it's a free MySQL instance with some limitations, but very usable for small sites. Setting it up is simple: enable it by setting a switch to On and Azure does the rest. You even get a phpAdmin-instance to configure your server! Sounds like a good deal. More information here.

To help you connect to this free MySQL instance, Azure defines an environment variable called MYSQLCONNSTR_localdb that you're supposed to be able to use. Spoiler: it's not.

The connection string set in MYSQLCONNSTR_localdb has the following format:

Data Source=localdb;Server=;User Id=azure;Password=some_password

If you try to Open() a MySqlConnection using this connection string will get an error message "No such host". I tried for hours to change my code to get it to work but it won't ever. The correct connection string is:


In other words:

  1. Don't use Data Source=, but Server=
  2. Split the port number (here: 49312) and the colon off into Port=
  3. Change UserId= into Uid= and Password= into Pwd=

Maybe only some of these steps are absolutely necessary, but this particular transformation works for me ;-)

You're welcome.

Update: I've found that User ID and Password work just fine, so I've resorted to changing Data Source= to Server=;Port=