|DataDirectory| in connection string

From
http://social.msdn.microsoft.com/Forums/en-US/sqlce/thread/dc31ea59-5718-49b6-9f1f-7039da425296

|DataDirectory| (enclosed in pipe symbols) is a substitution string that indicates the path to the database. It eliminates the need
to hard-code the full path which leads to several problems as the full path to the database could be serialized in different places.
DataDirectory also makes it easy to share a project and also to deploy an application.

For example, instead of having the following connection string:

"Data Source= c:\program files\MyApp\Mydb.sdf"

Using DataDirectory, you can have the following connection string:

"Data Source = |DataDirectory|\Mydb.sdf"

To set the DataDirectory property, call the AppDomain.SetData method. If you do not set the DataDirectory property, the following
default rules will be applied to access the database folder:

. For applications that are put in a folder on the user's computer, the database folder uses the application folder.
. For applications that are running under ClickOnce, the database folder uses the specific data folder that is created.