As mentioned in Chapter 2, Exploring the Top New Features of the CLR, .NET 4.5 is an in-place replacement for .NET 4.0, which only runs on Windows Vista SP2 or later systems.

This means that when .NET 4.5 is installed, it replaces the .NET 4.0 assemblies; even though .NET 4.5 has very high compatibility with .NET 4.0 scenarios, it might behave differently.

This comes along with the possibility that one of the deployment targets might not be supported by .NET 4.5, such as Windows XP.

Along the same lines, we can install Visual Studio 2012 in our machine along with Visual Studio 2010; they can be run side by side.

Next we will see these points and their risks in some detail, specifically mentioning the following:

Additionally, we will expose some risk points to keep in mind while developing with the .NET 4.5 framework.