This is a bit of a rant with hopefully a fix that will help others. Firstly, the rant:
In my post on Building Cross Platform Apps I used the new project templates in Visual Studio 2017 to create a new Xamarin.Forms application that targets iOS, Android and UWP. What I didn’t mention is the time I wasted trying to upgrade NuGet packages in order to get the thing to build and run. Namely I get the following exception when attempting to build the newly created application.
Severity Code Description Project File Line Suppression State
Error Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly ‘Xamarin.Android.Support.v7.RecyclerView, Version=1.0.0.0, Culture=neutral, PublicKeyToken=’. Perhaps it doesn’t exist in the Mono for Android profile?
File name: ‘Xamarin.Android.Support.v7.RecyclerView.dll’
at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters)
at Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences(DirectoryAssemblyResolver resolver, ICollection`1 assemblies, AssemblyDefinition assembly, Boolean topLevel)
at Xamarin.Android.Tasks.ResolveAssemblies.Execute(DirectoryAssemblyResolver resolver) App5.Droid
I figured that there was something wrong with the Xamarin.Forms and/or Xamarin Android NuGet packages, so I thought I’d just go an upgrade the Xamarin.Forms NuGet package. Note: Don’t every try to upgrade the Xamarin Android packages independently – let the Xamarin.Forms NuGet package determine which versions of those libraries you need. Anyhow, unfortunately that just generates another exception:
Severity Code Description Project File Line Suppression State
Error Unable to resolve dependencies. ‘Xamarin.Android.Support.Compat 24.2.1’ is not compatible with ‘Xamarin.Android.Support.Design 24.2.1 constraint: Xamarin.Android.Support.Compat (= 24.2.1)’. 0
At this point I was starting to get annoyed – it looks like there was already an inconsistency between the Xamarin.Forms package and the Xamarin Android packages included in the template. Luckily it was easier to fix than I thought it was. I opened up the packages.config file for the Android head project and delete the Xamarin.Android libraries.
<?xml version=”1.0″ encoding=”utf-8″?>
<packages> <package id=”Xamarin.Android.Support.Design” version=”23.4.0.1″ targetFramework=”monoandroid60″ />
<package id=”Xamarin.Android.Support.v4″ version=”23.4.0.1″ targetFramework=”monoandroid60″ />
<package id=”Xamarin.Android.Support.v7.AppCompat” version=”23.4.0.1″ targetFramework=”monoandroid60″ />
<package id=”Xamarin.Android.Support.v7.CardView” version=”23.4.0.1″ targetFramework=”monoandroid60″ />
<package id=”Xamarin.Android.Support.v7.MediaRouter” version=”23.4.0.1″ targetFramework=”monoandroid60″ />
<package id=”Xamarin.Forms” version=”2.3.2.127″ targetFramework=”monoandroid60″ />
</packages>
Then, I just upgraded Xamarin.Forms to the latest NuGet package and all was good again. Lastly, I upgraded all the other NuGet packages (excluding the Xamarin.Android packages) to the latest stable versions.