Hello, I'm having trouble with variables for connection strings. In my app.config database path seems fine but on form, I'm getting error for that connection string. When I try to add:

C# Code:
  1. _connectionString = "Data Source = (LocalDB)\\MSSQLLocalDB; " +

  2.         "AttachDbFilename = \"|DataDirectory|\\gazi_db.mdf\"; " +

  3.         "Integrated Security = True; Connect Timeout = 30";

the database won't work correctly; it can't save data on exit. However this Works fine:

C# Code:
  1. connectionString = "Data Source = (LocalDB)\\MSSQLLocalDB; " +

  2.         "AttachDbFilename = \"C:\\Users\\Can\\Desktop\\c_sharp_gazi_installer" +

  3.         "\\Gazi Installer\\gazi_installer\\gazi_db.mdf\"; " +

  4.         "Integrated Security = True; Connect Timeout = 30";

How can I fix this?