将 Visual Studio 2017 更新到版本 15.5.2 后出现 Xamarin 错误

Question

After updating my VS 2017 to the latest version, when I create a new Xamarin app it loads with errors. The surprising bit is that when I open an app created before I updated the IDE, it loads perfectly. Can anyone help? Below are the errors:

Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0012  The type 'AppCompatActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'Xamarin.Android.Support.v7.AppCompat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Error   CS0103  The name 'InitializeComponent' does not exist in the current context    App2ButtonImages.iOS    D:\Kajambiya\2017\Xamarin\App2ButtonImages\App2ButtonImages\App2ButtonImages\App.xaml.cs    14  Active.
Error   NU1202  Package Xamarin.Android.Support.v7.MediaRouter 25.4.0.2 is not compatible with monoandroid60 (MonoAndroid,Version=v6.0). Package Xamarin.Android.Support.v7.MediaRouter 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0)
Error   NU1202  Package Xamarin.Android.Support.v7.CardView 25.4.0.2 is not compatible with monoandroid60 (MonoAndroid,Version=v6.0). Package Xamarin.Android.Support.v7.CardView 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0)               
Error   NU1202  Package Xamarin.Android.Support.v7.AppCompat 25.4.0.2 is not compatible with monoandroid60 (MonoAndroid,Version=v6.0). Package Xamarin.Android.Support.v7.AppCompat 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0) 
Error   NU1202  Package Xamarin.Android.Support.v4 25.4.0.2 is not compatible with monoandroid60 (MonoAndroid,Version=v6.0). Package Xamarin.Android.Support.v4 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0)
Error   NU1202  Package Xamarin.Android.Support.Design 25.4.0.2 is not compatible with monoandroid60 (MonoAndroid,Version=v6.0). Package Xamarin.Android.Support.Design 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0)

Answer 1

I think at least the first errors speaks for it self, you need to add the nuget package

Xamarin.Android.Support.v7.AppCompat

The other errors point towards needing to build against a newer Android SDK, which you probably don't have installed.

Answer 2

我已经从 NuGet 卸载了所有 AppCompatActivity 包，它对我有用