For some reason this connection string is working with node js and this is an application user:

var http = require("http");

const sql = require("mssql");

const port =3333;

sql.connect('Server=B-SG-SQ;Database=DevTest;User Id=sg\\DevtestB;Password=DevtestB123;Encrypt=true;trustServerCertificate=true')
.then((conn) => {
  console.log(conn);
console.log("MSSQL: connected");

conn.query(`select * from samples`)
.then(data => console.log(data))
.then(() => conn.close())
}).catch(err => { console.log("err " + err) });

And I can see the list of objects from my table.

But when I try it with an ASP.NET Core 7 Web API:

public class DataContext
{
    private readonly DbSettings _dbSettings;

    public DataContext(IOptions<DbSettings> dbSettings)
    {
        _dbSettings = dbSettings.Value;
    }

    public IDbConnection CreateConnection()
    {
        var connectionString = "Server=B-SG-SQ;Database=DevTest;User Id=sg\\DevtestB;Password=DevtestB123;Encrypt=true;TrustServerCertificate=true";
        return new SqlConnection(connectionString);
    }
}

This is the result that I see:

Login failed for user 'sg\DevtestB'