זה הזמן לעבור לCode first
EF7 will not support the designer-based EDMX model. It will not have the ability to read the EDMX XML at run time to create the in-memory model. It will use only the Code First workflow.
https://msdn.microsoft.com/en-us/magazine/dn890367.aspx
https://msdn.microsoft.com/en-us/magazine/dn890367.aspx