[Mobile] Opening *.Android.sln / *.iOS.sln freezes visual studio

Release Type: GitHub

Version: e6f55ee3ed4c97173a5353faa03fe7686632b7ed

Platform(s): Windows

Describe the bug
When I try to open Xenko.Android.sln in Visual Studio it never finishes loading and locks. I can't build the assemblies for Android.

I'm not interested in iOS development for now but I tested Xenko.iOS.sln too and it has the same problem. The other solutions open fine.

I tried msbuild instead from the Developer Command Prompt for VS 2019:

msbuild Xenko.Android.sln /t:Rebuild
msbuild Xenko.iOS.sln /t:Rebuild

And they gives this error:

Xenko.Android.sln:

"F:\Xenko\xenko\build\Xenko.Android.sln" (Clean;Build target) (1) ->
"F:\Xenko\xenko\build..\sources\engine\Xenko.UI\Xenko.UI.csproj.metaproj" (Clean target) (2) ->
"F:\Xenko\xenko\build..\sources\engine\Xenko.Engine\Xenko.Engine.csproj.metaproj" (Clean target) (3) ->
"F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj" (Clean target) (11) ->
"F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj" (Clean target) (11:5) ->
(ResolvePackageAssets target) ->
C:\Program Files\dotnet\sdk\3.0.100\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(234,5): error NETSDK1005: Assets file 'F:\Xenko\xenko\sources\engine\Xenko.Engine\obj\project.assets.json' doesn't have a target for 'MonoAndroid,Version=v8.1'. Ensure that restore has run and that you have included 'monoandroid81' in the TargetFrameworks for your project. [F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj]

Xenko.iOS.sln:

"F:\Xenko\xenko\build\Xenko.iOS.sln" (Rebuild target) (1) ->
"F:\Xenko\xenko\build..\sources\engine\Xenko.Engine\Xenko.Engine.csproj.metaproj" (Rebuild target) (2) ->
"F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj" (Rebuild target) (11) ->
"F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj" (Clean target) (11:5) ->
(ResolvePackageAssets target) ->
C:\Program Files\dotnet\sdk\3.0.100\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(234,5): error NETSDK1005: Assets file 'F:\Xenko\xenko\sources\engine\Xenko.Engine\obj\project.assets.json' doesn't have a target for 'Xamarin.iOS,Version=v1.0'. Ensure that restore has run and that you have included 'xamarinios10' in the TargetFrameworks for your project. [F:\Xenko\xenko\sources\engine\Xenko.Engine\Xenko.Engine.csproj]

To Reproduce
Steps to reproduce the behavior:

1. Open Xenko.Android.sln in Visual Studio 2019.

Expected behavior
Build Xenko.Android.sln so I can build and run a game project for an Android device.

Start by reproducing the failure with build/Xenko.Android.sln and build/Xenko.iOS.sln in Visual Studio 2019 or with the listed msbuild commands. Inspect sources/engine/Xenko.Engine/Xenko.Engine.csproj and the reported obj/project.assets.json target errors. Done means both platform solutions open and build successfully without freezing or NETSDK1005 errors.