I am following a tutorial of model-first approach in ASP.NET MVC in which I am using ADO.NET Entity Model Data, empty EF designer model and when generating the database after defining it's properties getting an error

An Item with the same key has already been added

Here's my model:

My Model

And this is a error I get:

Couldn't generate DDL, Error

I tried rebuilding the solution and making sure that the model doesn't have duplicate keys.

Update - Just tried the same in a different folder and it worked.