The samples and blog posts I have published on building ASP.Net MVC web applications that consume Office 365 APIs have used the OWIN Katana middleware for authentication.
Many folks have asked me how Office 365 APIs work, how does it interact with Azure AD, authenticate users and authorize applications.
Office 365 Discovery Service helps you to discover the available service capabilities for your app along with the respective service resource Ids and endpoint URIs.
One of the key (and the most important) steps for your application to consume Office 365 APIs is to register an Azure Active Directory application in your Office 365 subscription tenant for that application and configure access to specific Office 365 APIs (mail, calendar, contacts, my files etc.,) The Problem However, accessing your Office 365 subscription’s tenant directory from the Azure Active Directory (AD) portal has been a painful task that you had to link it to an existing Azure subscription and that you have to login with your Microsoft Account and not with Office 365 subscription account also complicates things when accessing the Azure Active Directory portal.
If you are looking for cross-platform development within Visual Studio, Xamarin is a great option to build applications not just for Windows, also for iOS and Android devices in C#, the language we all love.
Now that Office 365 APIs are generally available, you would want to go integrate Office data into your applications and are looking for resources for you to get started.