Reading config file from Orchestration

I have a biztalk project  named "InfoReader" which has an orchestration. This orch reads the config file in th expression shape using the code as shown below

EmpID = System.Configuration.ConfigurationManager.AppSettings["EmpId"];

EmpSSN = System.Configuration.ConfigurationManager.AppSettings["EmpSsn"];

where EmpID and EmpSSN are orchestration variables.

Now, my InfoReader.dll.config looks like this

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <appSettings>
        <add key="EmpId" value="100" />
        <add key="EmpSsn" value="111-22-3333" />
    </appSettings>
</configuration>

When I run my orchestration, I am getting exception below

Uncaught exception (see the 'inner exception' below) has suspended an instance of service 'InfoReader.ReadConfigOrchestration(487d0f7f-1ae1-c847-847e-e438a8ab2117)'.
The service instance will remain suspended until administratively resumed or terminated.
If resumed the instance will continue from its last persisted state and may re-throw the same unexpected exception.
InstanceId: d31a5f64-ce4d-4970-a9ee-e9581c9de2a1
Shape name: ConstructMessage_1
ShapeId: 50f5c442-44d0-4781-952e-6d7b4b4f2f3a
Exception thrown from: segment 1, progress 12
Inner exception: Value cannot be null.
Parameter name: val

For some reason, the code in the expression fails to read the config file.

What should be the name of the config and where should I put it ?

(Right now the config file (InfoReader.dll.config) is in ..\bin\development\ directory the same place where my orchestration dll is )

Any help on this is greatly appreciated.

(Sorry for the long post… 🙂 just wanted to give you guys every minute detail )