Though a lot of third-party services exist for in-app purchasing on Windows Phone, Microsoft might be adding it soon officially. There a couple of hints which suggest this. There's a Vimeo video by Silvertail software from the Portland Code Camp about monetization for developers in which Kelly White remarks that in-app purchasing is on the way. Another is the agenda of Microsoft's Gamefest sessions in London which talks about Micro-Transactions and Downloadable Content. The agenda summary makes it seem like an Xbox Live feature but we will wait for more details before making a decision.
Keep Them Coming Back: Downloadable Content on Windows PhoneSpeakers: Darryl Yust and Tim GillCome learn proven approaches for dealing with some of the toughest hurdles in adding downloadable content and microtransactions to your Windows Phone games! This talk introduces the new in-game purchase API for Xbox LIVE titles on Windows Phone. We'll get down to the nitty-gritty of how the API is used in Beards & Beaks, a shipped game title. We’ll delve into a sample code framework that helps you implement game-side functionality not included in the SDK library, including the handling of file transfers, tombstoning, serialization, offline scenarios, localization, content ingestion, and fast content iteration.
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