Create a new project (e.g. C# console project)
Using the project's properties change the target framework to .NET 4.0
Create an empty ADO.NET Entity Data Model
Add 1 Entity with 1 property
Save everything (you will have a V2 EDMX because targeting .NET 4.0)
_Keeping the EDMX file open in the designer_ change the target framework to .NET 4.5
You will receive the info message that the namespaces have been updated _but_ the designer for the EDMX will be in "safe mode" - showing that it is unable to display the file. If you open this file in the XML Editor you will see that the namespaces have not in fact been changed.
Using the project's properties change the target framework to .NET 4.0
Create an empty ADO.NET Entity Data Model
Add 1 Entity with 1 property
Save everything (you will have a V2 EDMX because targeting .NET 4.0)
_Keeping the EDMX file open in the designer_ change the target framework to .NET 4.5
You will receive the info message that the namespaces have been updated _but_ the designer for the EDMX will be in "safe mode" - showing that it is unable to display the file. If you open this file in the XML Editor you will see that the namespaces have not in fact been changed.