Visual Studio Community 2019 Update affects Xamarin

Question

I have a big problem with Visual Studio Community 2019 V16.9.0. I have installed this update and when I tried to run again my Xamarin.Android project it's led to crash. I have tried to make a new project, the name was auto-generated "App3" because I don't want to modify anything in order to see that the project can be built successfully. The build failed as you can see in the picture below.

VS also can't see the References for the project.

I have tried to repair the SDK but it doesn't help because the reparation has failed.

I let you als the errors that had been generated.

Build started...
Starting emulator Nexus_5X_API_29 ...
1>------ Build started: Project: App3, Configuration: Debug Any CPU ------
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004: System.ArgumentException: Illegal characters in path.
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at System.IO.Path.CheckInvalidPathChars(String path, Boolean checkAdditional)
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at System.IO.Path.Combine(String path1, String path2)
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.ProcessUtils.<FindExecutablesInDirectory>d__9.MoveNext() in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/ProcessUtils.cs:line 177
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.ProcessUtils.<FindExecutablesInPath>d__8.MoveNext() in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/ProcessUtils.cs:line 168
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkBase.<GetAllAvailableAndroidNdks>d__73.MoveNext() in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkBase.cs:line 153
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkWindows.<GetAllAvailableAndroidNdks>d__43.MoveNext() in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkWindows.cs:line 257
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkBase.GetValidNdkPath(String ctorParam) in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkBase.cs:line 128
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkBase.Initialize(String androidSdkPath, String androidNdkPath, String javaSdkPath) in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkBase.cs:line 71
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkWindows.Initialize(String androidSdkPath, String androidNdkPath, String javaSdkPath) in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkWindows.cs:line 310
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tools.AndroidSdkInfo..ctor(Action`2 logger, String androidSdkPath, String androidNdkPath, String javaSdkPath) in /Users/builder/azdo/_work/278/s/xamarin-android/external/xamarin-android-tools/src/Xamarin.Android.Tools.AndroidSdk/AndroidSdkInfo.cs:line 18
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tasks.MonoAndroidHelper.RefreshAndroidSdk(String sdkPath, String ndkPath, String javaPath, TaskLoggingHelper logHelper)
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tasks.ResolveSdks.RunTask()
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Tooling.targets(64,5): error XARSD7004:    at Xamarin.Android.Tasks.AndroidTask.Execute()
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
========== Deploy: 0 succeeded, 0 failed, 0 skipped ==========

Answer 1

Check your system PATH environment variable in Windows System Advanced Settings. I had the same issue. After few days seeking for solution I noticed a strange empty entry in PATH. After deleting it the error XARSD7004 is finally gone... The bug was probably casued by VS 2019 16.9,2 update in my case, I wrote this solution for others not to loose few days fighting it like me. I reinstalled Xamarin, SDK, tried tons of different settings and even thought of reinstalling whole VS.