Microsoft on Monday also announced the – Silverlight 4, Expression Blend 4 beta, Visual Studio 2010,and XNA – for Windows Phone developers to begin designing, writing and testing mobile applications.

The move is clearly intended to spark widespread interest in porting existing applications, and writing new ones, for the redesigned mobile OS. Microsoft has been heavily focused on managed code development. 

During a post-keynote briefing with reporters, Brian Goldfarb, Lead Product Manager of the Web Platform and Tools at Microsoft, said that as a result of today’s announcement, “Overnight, over 500,000 Silverlight developers became Windows Phone developers.”

Microsoft officials cited external and internal studies that show Silverlight currently is present on 60% of all Internet-connected devices.

The new UI for Windows Phone, coupled with a minimum hardware platform that’s mandated for the wave of devices expected starting in fall 2010, create a far more consistent mobile development platform for Microsoft coders. The new hardware specification, mandates just two screen resolutions, a common applications process, separate graphics processing unit, flash and memory minimum requirements. Handset makers can add to these, said Brix, but they cannot subtract from them or change them.