UI OVERHAUL AND VISUAL STUDIO

A very commendable move by Microsoft. Gone are the days of MorphX IDE. Welcome Visual Studio (VS) for all your development work. It is a complete UI, which will help you provide an improved hand-user experience.
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EXTENSIONS

There is a lot to learn now, as Visual Studio is the new IDE for Dynamics 365 development work. One of the very first things to learn will be extensions. Previously, there was an option for the developers to modify the existing object but now, there is no such option. The developer will have to create an extension of the object and then perform the customizations. This will not affect the existing system object thereby paving way for easy future upgrades.
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INTEGRATION / DATA ENTITIES

Integration has also undergone a major change. Now it is called ‘Data entities’. Data entities is a common framework for DIXF and AIF web service. The developer will have to take extra precautions while upgrading from AX 2012 as in Dynamics 365 the web services have become in a restful state with JSON-formatted data. So existing customization (in older versions of AX) related to integration will go for a complete change.