Error XF001: Xamarin.Forms targets have been imported multiple times

If you’re in the process of updating a Xamarin.Forms app to a more modern style project set up (NET Standard 2.0, PackageReference, etc), you may get the following error.

 

Error XF001: Xamarin.Forms targets have been imported multiple times. Please check your project file and remove the duplicate import(s).

 

This can be because of the move to using PackageReference for your NuGet packages and a simple fix awaits you.

  1. Close Visual Studio and navigate to the Solution in File Explorer
  2. Delete the hidden .vs folder
  3. Go into each affected project sub folder and delete the following files; project_name.nuget.props and project_name.nuget.targets
  4. Open the solution in Visual Studio, do a Clean and Rebuild, 

 

You should no longer see the error and be able to deploy.

 

 

 

 

Migrating from PCLStorage to .NET Standard 2.0

If you’re a Xamarin Forms developer, you’ve likely used PCLStorage (or other Dependency Service) to interact with the target platform’s file system in the portable class library’s code. However, since November 2017, Xamarin.Forms now uses a .NET Standard 2.0 class library and PCLStorage is no longer supported.

System.IO.File

This isn’t a problem because in .NET Core 2.0 you now have access to System.IO.File’s GetFolderPath and SpecialFolder methods (see System.IO.File in .NET Core 2.0 docs).

Thus, you can get a path to the app’s local folder (the one that the app can save to) without having to write a Dependency Service (which is what PCLStorage does) by using:

var localFolder = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);

 

IMPORTANT: Make sure you always use Path.Combine to create the file path because different platforms use different path separators

var filePath = Path.Combine(LocalFolder, "notes.txt");

 

With a reference to the file path,  you can now access the file. For example reading the text:

var notes = File.ReadAllText(filePath);

Functional Demo

As a very simple example, I created a couple extension methods for Stream and Byte[] in the below FileExtensions class.

To test it, I created a ContentPage that downloads an image, saves it using the extension method and set a FileImageSource to confirm that it’s a file (instead of just using a StreamImageSource).

 

https://gist.github.com/LanceMcCarthy/693ab82aa498cadf75e9fe778c4242ad

 

Note that the extension methods are very basic and shouldn’t be used in production as-is (i.e. no defensive programming code).

Here is the result at runtime on UWP:

2018-04-19_1134