How does the CurrentApp.ReportProductFulfillment method work?

Question

I'm testing my Windows Phone 8 app for scenarios where my app goes to the background before it can fulfill a consumable purchase. So, on every app-launch I check if there are any unfulfilled in-app purchases, if there are, I fulfill them using the CurrentApp.ReportProductFulfillment method. However, while testing I noticed this method works even if the device isn't connected to the Internet. So how and when does the app let the Marketplace know that the purchase has been successful? More importantly, should I only do this only if I have an Internet connection?

This is my code by the way :

var licenses = CurrentApp.LicenseInformation.ProductLicenses;
if (licenses["PRODUCT_ID"].IsConsumable && licenses["PRODUCT_ID"].IsActive) {
    // Fulfill consumable purchases

    // Let the Marketplace know
    CurrentApp.ReportProductFulfillment("PRODUCT_ID");
}

Answer 1

Marketplace communications occur on a background task spawned by the OS on regular intervals. You can observe this traffic if you attach Fiddler to a machine running Windows Phone emulator

The following statements are merely suppositions on my part, so take it with a grain of salt. I would imagine the background Marketplace communication handles a number of tasks. The most common of these would be checking for application updates. However, this would also be an ideal time for the OS to communicate fulfillment of an order. In that vein, Marketplace services likely queue your report request and, if it cannot be communicated immediately, defers it for the background task to handle at a later time, allowing the method to run even when the phone does not have data access. Given the nature of modern cashless transactions, I don't see any reason the Marketplace would require immediate notification of fulfillment, as it has time to complete a transaction once initialize authorization is acquired.