Faked values cached

I have a test where I am substituting a call to my DAL class with a call to a stub. Both return an IDataReader which is used internal to by business object.

Isolate.WhenCalled(() => fakeDal.GetItemNumbersFromProduction()).WillReturn(new SingleItemNumbersStub().GetDataReaderStub());

When testing my ModelView code, the GetItemNumbersFromProduction is called twice. Once upon creation of the ModelView, and again after a save operation (other methods on the fakeDal are also called as part of the process of creating the MV). After the Save is where I am seeing a problem in that it appears that the IDataReader returned from the above code is cached, and again used for the second call to the faked method. However at this point the data reader is closed and so an exception is thrown.

Is there a way to use Isolater such that every time the fakeDal.GetItemNumbersFromProduction() method is called, the WillReturn is re-evaluated, causing a new data reader to be returned?

Isolate.WhenCalled(() => fakeDal.GetItemNumbersFromProduction()).DoInstead(callContext => { return new SingleItemNumbersStub().GetDataReaderStub(); });