Portable Class Library System.Object error

Question

I am using Portable Class Libraries (PCL) in Xamarin Studio on OS X. I have two PCL libraries that are targeting .NET 4.5, Windows Phone 8, Windows Store Apps, Xamarin.iOS, and Xamarin.Android. I reference these two libraries in my iOS, Android, and Unit tests projects. In 3 areas I am getting the following error:

The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

The code is straightforward:

MyClass myClass = new MyClass();

The error occurs once in each of the projects that reference the PCLs. None of them are the same class. I am new to PCLs. I've tried removing the Windows Phone 8 (as I added it last minute) and yet the problem does not go away. Any help would be appeciated!

Thanks!

Update:

So this occurs with the first field declared in the class (where the class is from the PCL project).

int a = 0;
MyPCLClass _myPCLClass = new MyPCLClass();  //This is where the error appears

Another odd aspect is that there are over 50 classes using these classes, and the error is only appearing in three classes.

Answer 1

I just ran into this exact same problem, and have the same setup as you do. A tip mentioned in a comment (by Stuart, which in turn mentioned a tweet by @DavKean) to this question solved it for me.

You have to:

• access a Windows machine (I used a Windows 8)
• grab C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\Facades\System.Runtime.dll
• copy it to your Mac
• add a reference to this dll from each of your iOS and Droid projects