I could not see below Class Diagrom button on VS2013. Was this option excluded from VS2013. Where is Class Diagram on Visual Studio 2013.
There is a Map Code button in VS2013 but as my understanding it is not working like Class Diagram. Actually I don't understand how it works.
You add a Class Diagram the same way you add any other new project item, i.e. right-click the project and select Add -> New Item.