In a Portable Class Project in Visual Studio 2013, when I select
Visual Studio claims that Silverlight 5 supports every available functionality that is portable between the other frameworks I selected and selects it automatically. But it's wrong because I need to use /unsafe compiler option which is not possible in Silverlight applications.
I select .NET Framework 4.5 instead of 4 as a workaround, so Visual Studio doesn't select Silverlight 5 automatically, but it shouldn't be needed since the project is perfectly compatible with .NET Framework 4 as well.
How can I get around that?
Is there anything I can change in the project file, like ProjectTypeGuids?
Well, you certainly can get around it. It just takes a bit of surgery on the .csproj file for the PCL project. Open it in a text editor, Notepad will do fine, and add this line to the <PropertyGroup>, after the ProjectTypeGuids property:
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
Which is enough to fool MSBuild and the compiler to allow you to use unsafe code.
I can't think of any failure scenario, you won't lose that property either when you make changes in the PCL project and rewrite the .csproj file. Your only nemesis could be a hyper-active Store validator that will reject your app, I consider the odds very low since unsafe code is otherwise fine. Just don't use it in a Silverlight project :)