In VS2013 this isn't settable within VS itself.
To view the target framework
Project Properties > Common Properties
Ifa target framework is set (not all applications need it) then it is displayed above the right side main box(es).
To set / change a target framework
Close the project.
Open the projects .vcxproj with notepad. Find the "<PropertyGroup Label="Globals">" section:
<PropertyGroup Label="Globals">
<ProjectGuid>{DF740E12-4588-4559-9BC6-761AF5F99AA4}</ProjectGuid>
<RootNamespace>Hycal_PC_Software</RootNamespace>
<Keyword>ManagedCProj</Keyword>
<TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
</PropertyGroup>
If not <TargetFrameworkVersion> entry is found then you can add it here, and if it is then change the value here. Close the file, re-open the project and verify the new framework version is shown in Project Properties.
