I guess you are missing database name in the connection string.
SqlConnection con = new SqlConnection(@"Data Source=IVY\SQLEXPRESS;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False");
try it by putting the name of your database in the following string.
SqlConnection con = new SqlConnection(@"Data Source=IVY\SQLEXPRESS; Initial Catalog=YOUR_DATABASE_NAME;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False");