This connection string would create a data source is called ConnectOracle, used to connect to the Oracle database TestDB:
<connectionStrings>
<add name="ConnectOracle" connectionString="Data Source=TestDB;User Id=username;Password=password"providerName="Oracle.ManagedDataAccess.Client"/>
</connectionStrings>
Similarly, this example would connect to the same database, but it would use OS Authentication instead of database user authentication:
<connectionStrings>
<add name="ConnectOracle" connectionString="Data Source=TestDB;User Id=/" providerName="Oracle.ManagedDataAccess.Client"/>
</connectionStrings>
The following example would connect to the same database, but it uses the connect descriptor for the Oracle database:
<connectionStrings>
<add name="ConnectOracle" connectionString="Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=hostname)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=TestDB)));User Id=username;Password=password" providerName="Oracle.ManagedDataAccess.Client"/>
</connectionStrings>
Tip:
In order to ensure that the required system settings take effect, it is a best practice to restart the installing machine once the installer has finished.