Question

In AppConfig it is possible to use |DataDirectory| but I can’t find any doc ?

Answer 1

|DataDirectory| is a substitution string so you can configure the location of your database file separately.

So instead of:

SqlConnection c = new SqlConnection (
   @"Data Source=.\SQLDB; AttachDbFilename=C:\MyDB\Database.mdf;Initial Catalog=Master");

you do the following:

// Set |DataDirectory| value
AppDomain.CurrentDomain.SetData("DataDirectory", "C:\myDB");

// SQL Connection String with |DataDirectory| substitution string
SqlConnection c = new SqlConnection (
   @"Data Source=.\SQLDB; AttachDbFilename=|DataDirectory|\Database.mdf;Initial Catalog=Master");