1) Private Function testGetTotal(ByVal idEntities As Integer, ByVal RefDate As Date) As IQueryable(Of Tbl_Contract)
        Dim returnValue = From contract In db.Tbl_Contracts _
               Where (contract.EndDate >= RefDate And contract.NextDuesInvoice <= RefDate Or contract.NextDuesInvoice Is Nothing) _
                      And (contract.NumMonthsPaid < contract.TermMonths) And (contract.idContractStatus = 1) And (contract.idEntity = idEntities) _
               Select contract


        Return returnValue.AsQueryable()
    End Function

2) Private Function TESTTHISFUNCTION(ByVal contract As Tbl_Contract) As Tbl_Transaction

        Dim brTrans As New BRTransaction
        Dim Membership As Tbl_ContractProduct
        Dim EndDateFromContract As DateTime

        For Each contract In testGetTotal(46, Date.Now()) ' Find ValidContract
            ' Cycle through valid contracts (loop)

            Dim taxes = brTrans.GetTaxesPercent(PublicProperties.userLoggedEntity.idEntity, contract.idContact)
            'Dim MembProd = (From p In db.Tbl_Products Where p.idProduct = Membership.idProduct).Single
            Dim DepositSQL = (From m In db.Tbl_ContractProducts _
                           Where m.idContract = contract.idContract _
                             And m.IdContractRelType = Grav_ContractRelationshipType.Deposit).SingleOrDefault
            Dim Deposit As Decimal
            Deposit = 0

            'If (MembProd.membershipExpierType = 1) Then
            '    EndDateFromContract = MembProd.expiryDate
            'Else
            '    EndDateFromContract = Today.AddMonths(MembProd.membershipLength)
            'End If
            ' Add new Contract
            db.MakeNewContract(PublicProperties.userLoggedEntity.idEntity, PublicProperties.userLoggedEntity.idEntity, contract.idContact, Date.Now, _
                               PublicProperties.idContactUser, Date.Now, PublicProperties.idContactUser, _
                               Grav_ContractStatus.Pending, EndDateFromContract, 0, False, False, False, taxes.LabelTax1, _
                               taxes.LabelTax2, taxes.LabelTax3, taxes.idGLTax1, taxes.Tax2, taxes.idGLTax3, Deposit, 0, 0, 0, _
                               taxes.Tax1, taxes.Tax2, taxes.Tax3, 0, 0, 0, 0, 0, ((contract.SubTotal - contract.Deposit) / contract.TermMonths), _
                               0, 0, 0, Nothing, Nothing, False, False, 0, 0, 0, Nothing, Nothing, 0, Nothing, Nothing, Nothing, Nothing, _
                               Nothing, Nothing, False, Nothing, contract.EndDate, Nothing, Nothing, 0, 0, 0, False, 0, 0, False, _
                               0)

        Next contract  ' End loop
    End Function


And calling the function I do this:

   TESTTHISFUNCTION(CType(testGetTotal(46, Date.Now()), Tbl_Contract))

but I get this error message after testgettotal function is completely executed

Unable to cast object of type 'System.Data.Linq.DataQuery`1[SoDBLogic.Tbl_Contract]' to type 'SoDBLogic.Tbl_Contract'.