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Visual Studio 2013 Preview shipped with support to create new ASP.NET projects that can be easily configured with organizational accounts. This support has been simplified and enhanced in this RC version. You can find a detailed step-by-step tutorial on creating an ASP.NET MVC project with single organizational identity at Developing ASP.NET Apps with Windows Azure Active Directory.
The biggest change in this release is the addition of support for configuring ASP.NET WebAPI project with Windows Azure Active Directory identity. For more information on changes done in RC release, you can look at What’s New for Organizational Accounts in Visual Studio 2013 RC