Toni codes .NET

Portable classes in Visual Studio 2012 are simply awesome. They allow high code reuse for multiple platforms. Another great addition in Visual Studio 2012 is support for asynchronous programming in C# 5 which, sadly, was not initially available for Windows Phone 7 developers.

If you want to target Windows Phone 8 and Windows Store, you can use Async if you also target .NET 4.5. If you want to target Windows Phone 7.1 and Windows Store, you cannot use asynchronous features from C# 5. But with the prerelease version of Async for .NET Framework 4, Silverlight 4 and 5, and Windows Phone 7.5 and 8 you can finally use Async in your Windows Phone 7 applications. If you want to target largest market, you need to support Windows Phone 7 along with Windows Phone 8, it is too large to simply ignore.

So, can we use Async in portable libraries while still targeting both Windows Phone 7 and Windows Store? Luckily, the answer is yes. But, and there is always a but, with one caveat – you must target .NET 4.0 instead of .NET 4.5.

The procedure is simple: create a new Portable Class Library and select the targets as seen on the image below:

Portable Class Library targets

To add Async support, run the following command in the Package Manager Console:

Install-Package Microsoft.Bcl.Async -Pre

Voila, you can now write asynchronous code in a portable class library which can then be linked in Windows Phone 7, Windows Phone 8 and Windows Store projects. If you build a Windows Phone 7 application and link to such portable class library, you will need to add the same NuGet package to that project also.

Last updated by Toni at 27/02/2013.