SQL Express connection string: mdf file location relative to application location

Question

I am using SQL Express databases as part of a unit test project in c#. My databases is located here:

./Databases/MyUnitTestDB.mdf

I would like to use a relative path or variable in the app.config rather than having my connection string defined as:

AttachDbFilename=C:\blah\blah\blah\yea\yea\yea\MyApplication\Databases\MyUnitTestDB.mdf 

I have seen the use of |DataDirectory| but am I correct in thinking this is only applicable to web applications?

I want to control this in the application configuration file, as in production the application uses a hosted sql database.

Answer 1

Thanks everyone, I used a combination of your responses.

In my app.config file my connection string is defined as follows

<add name="MyConnectionString"
    connectionString="Server=.\SQLExpress;AttachDbFilename=|DataDirectory|\MyDatabase.mdf;Database=MyDatabaseForTesting;Trusted_Connection=Yes;" />

In my unit test class I set the DataDirectory property using the following

[TestInitialize]
public void TestInitialize()
{
    AppDomain.CurrentDomain.SetData("DataDirectory", System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Databases"));

    // rest of initialize implementation ...
}