Entlib + config problem

[C# Programming]

Hello All,

I've got a problem with EntLib 4.1 in combination with my config file.

I have a class library for data access which has its own app.config file containing the information for the sql connection.
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Code to access the database:
public static DataSet SelectAll()
{
DataSet retValue = new DataSet();

try
{
Database db = DatabaseFactory.CreateDatabase();
DbCommand cmd = db.GetStoredProcCommand(stpTest);
retValue = db.ExecuteDataSet(cmd);
}
catch (Exception ex)
{
throw ex;
}

return retValue;
}

With this go the following includes:
using System.Data;
using Microsoft.Practices.EnterpriseLibrary.Data.Sql;
using Microsoft.Practices.EnterpriseLibrary.Data;
using System.Data.Common;


What am i doing wrong, i'm getting the following error on the CreateDatabase() line:

{"The current build operation (build key Build Key[Microsoft.Practices.EnterpriseLibrary.Data.Database, null]) failed: The value can not be null or an empty string. (Strategy type ConfiguredObjectStrategy, index 2)"}