Everything is an error on VS2019 but not VS2017, why?

Question

Everything is an error on VS2019 but not VS2017, why?

Phunction 301

Hopefully someone can help, I have an android project, works fine with VS2017, but when I open it in VS2019 everything is red(ie: The type or namespace 'System' could not be found...).
All the references are shown with a yellow icon, unless I click on it then the icon goes away.
How do I track this down? Why does it work on 2017 but not 2019? I really need to get it to work on 2019 as 2017 is limited to Android 9.0 sdk.
I can't find any hint as to why it does not work, there is nothing in the Xamarin logs, if I try building I just get a build failed in the output window.

Cole Xia (Shanghai Wicresoft Co,.Ltd.) 6,756 Reputation points

2020-12-22T07:45:58.163+00:00
@Phunction

Here are some normal suggestions.

Delete the hidden .vs folder in your project folder .

Delete bin and obj folders in all sub folders.

Go C:\Users\xxx\AppData\Local\Microsoft\VisualStudio directory, you can find many 15.xx and 16.xx folders there, feel free to delete all ComponentModelCache folders in them and restart VS.

Update all packages to the latest in Nuget.

Clean and rebuild .

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Cole Xia (Shanghai Wicresoft Co,.Ltd.) 6,756 Reputation points

2020-12-22T07:45:58.163+00:00

@Phunction

Here are some normal suggestions.

Delete the hidden .vs folder in your project folder .

Delete bin and obj folders in all sub folders.

Go C:\Users\xxx\AppData\Local\Microsoft\VisualStudio directory, you can find many 15.xx and 16.xx folders there, feel free to delete all ComponentModelCache folders in them and restart VS.

Update all packages to the latest in Nuget.

Clean and rebuild .

Answer 1

Hello,

Welcome to Microsoft Q&A!

xamarin.googleplayservices.maps need dependencies of AndroidX , AndroidX is a replacement to the original Android Support Library , if you install both if them in your project , there will be conflict.

You can remove Support library and migrate to AndroidX package .

Check the details in this article : https://learn.microsoft.com/en-us/xamarin/android/platform/androidx

Thank you.

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Answer 2

Duane Arnold 3,216

All the references are shown with a yellow icon, unless I click on it then the icon goes away.

Then the project has none of the references to the DLL(s), like 'System' or any of the other DLL(s). I think you will need to use the Nuget's Restore feature to have the referenced DLL(s) restored to the project.

https://learn.microsoft.com/en-us/nuget/consume-packages/package-restore

Phunction 301 Reputation points

2020-12-22T20:30:06.143+00:00

I don't think this is the case as it works fine in VS 2017, doing a restore does not help.
Duane Arnold 3,216 Reputation points

2020-12-23T06:19:00.707+00:00

I don't think this is the case as it works fine in VS 2017, doing a restore does not help.

Well that is the case when you see the yellow exclamation point next to a reference is that the project in that particular version of VS has the reference broken. I have faced the problem too many times as companies I have worked for upgraded to a newer versions of VS.

Answer 3

Phunction 301

I removed all my nuget packages and the 'system' errors went away (still had errors that referenced the nuget packages.)
I then install the newer version of the nuget packages, namely Android.Support.V4 and google play services.
Now, when I first install Android.Support.V4, it is OK, however, when I then try to install xamarin.googleplayservices.maps, everything breaks again. I have to remove all nuget packages.

Is there a problem with running Android.Support.V4 and xamarin.googleplayservices.maps together?

Karen Payne MVP 35,586 Reputation points Volunteer Moderator

2020-12-22T21:35:24.983+00:00

I would post in the issue section for each package on GitHub

https://github.com/xamarin/AndroidSupportComponents/issues

https://github.com/xamarin/GooglePlayServicesComponents/issues
Phunction 301 Reputation points

2020-12-22T22:43:59.81+00:00

I think it is due to googleplayservices installing xamarin.androidx.xxx which also has a version of android.support.v4, however that version does not have android.support.v4.content which I seem to need for localbroadcastmanager.

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Everything is an error on VS2019 but not VS2017, why?

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