Scaffold problem

I am working on database first project and have some changes in a database so I tried to scaffold database objects but have an error that looks like this:

Format of the initialization string does not conform to specification starting at index 0.

This error is received through a window that has the label "Inferring data source" with a lot of following text that describe in a .NET manner what was going wrong.

As I did it several times before the same process I need to know what I have done wrong. Compiled application works with no problem and compilation is with no errors.

Probably the connection string to the database is wrong. Did you change anything in it? Password maybe?

That connection string is the very same string that application run with.

In that case we are not sure what went wrong. This message indicates a bad connection string.

Can you help me where can I find records that are in the section "Choose an existing data source" maybe I could solve the problem when I delete or edit them.

Those "records" are parsed from your source code. You can't delete them. You can try recreating the data source as a new one. Make sure to use the exact same name as before. I still think there is a problem with the connection string (which is stored in appsetings.json/appsettings.Development.json).