Using WPF Controls with the .NET 4 Framework

Our WPF controls are built to target .NET 3.5 SP1, but they can be used as-is by applications that target .NET 4. So as long as the application that references our WPF controls targets the .NET 4 framework, then our controls will load and run just fine.
Users that only have the .NET 4 framework installed (i.e. .NET 3.5 SP1 is not installed) will experience a problem running our Sample Browser after installing. Our Sample Browser was also built to target .NET 3.5 SP1, and, by default, will fail if only the .NET 4 framework is installed. There are two ways to retarget our Sample Browser to the .NET 4 framework.
The first option is to open the Sample Browser C# or VB.NET project in Visual Studio 2010 and configure it to target .NET 4. After this is done, the project must be recompiled to build a new version of the Sample Browser executable that looks for the .NET 4 framework.
Alternatively, a custom app.config file can be used to force the Sample Browser application to be loaded in the .NET 4 framework. To do this a text file named SampleBrowser.exe.config must be created in the same directory as the SampleBrowser.exe file, with the contents: 
    <supportedRuntime version="v4.0" />