Expressing Designs in C# - Effective C# - page 170

channel more than including orders in the customer download? We'll add
a few more assumptions on the business processes to give you some more
ideas. Suppose that the call center is partitioned so that each working team
receives calls from only one area code. Now you can modify your design
to optimize the communication quite a bit more.
Each operator would retrieve the updated customer and order information
for that one area code at the start of the shift. After each call, the client
application would push the modified data back to the server, and the server
would respond with all changes since the last time this client machine
asked for data. The end result is that after every phone call, the operator
sends any changes made and retrieves all changes made by any other oper-
ator in the same work group. This design means that there is one transac-
tion per phone call, and each operator should always have the right set of
data available when he or she answers a call. It has saved one round-trip
per call. Now the server contains two methods that would look something
like this:
public CustomerSet RetrieveCustomerData(
AreaCode theAreaCode)
{
// Find all customers for a given area code.
// Foreach customer in that area code:
// Find all orders by that customer.
// Filter out those that have already
// been received.
// Return the result.
}
public CustomerSet UpdateCustomer( CustomerData
updates, DateTime lastUpdate, AreaCode theAreaCode)
{
// First, save any updates.
// Next, get the updates:
// Find all customers for a given area code.
// Foreach customer in that area code:
// Find all orders by that customer that have been
// updated since the last time. Add those to the result.
// Return the result.
}