Entity framework power tools was a handy extension for this purpose. However, this tool is not working with VS 2015. So, I thought of creating a VS extension to generate data model diagram from a data context class.
The extension is now available at https://marketplace.visualstudio.com/vsgallery/98588731-ffa7-46ab-bdbf-101c63271779
Visual
studio extension code: https://github.com/ajopjo/Entity-Framework-Model-Generator
Since I lead some of the VS extension development at Allstate, it took around an hour to complete the task. Is it complete, no because I haven't wrote any test cases :)
happy coding!!!!