Building Android Xamarin.Forms Project on Windows Fails

Tony Pitman 76

I have a solution based on Xamarin Forms. I have included a library called Plugin.BluetoothLE. This project has several platform folders that target the different platforms. This includes Android, iOS and UWP.

When I build the Android target project on my Mac using Visual Studio 2019 for Mac everything builds just fine.

When I try to build the same project on my Windows 10 computer with Visual Studio 2019 it fails. Here is the error I am getting:

1>C:\dev\Software_mobile\Components\bluetoothle\Plugin.BluetoothLE\Extensions_Device.cs(169,13,171,28): error CS0012: The type 'IAsyncOperation<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows.Foundation.FoundationContract, Version=4.0.0.0, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.

Why is this library trying to include something from Windows? It should be cross platform when I build for Android and builds fine on MacOS VS2019.

How can I get this to build on Windows VS2019?

JarvanZhang 23,951 Reputation points

2021-10-22T05:56:19.647+00:00

Hi, TonyPitman-4374. Please open the Dependencies of the shared project to check if the Assemblies and Packages have a yellow warning triangle on it. If it is, try to remove it and reinstall the dll.

The dll is used in UWP project. If the above doesn't work, try to unload the UWP project and then build the Android platform to check if it would work.
Tony Pitman 76 Reputation points

2021-10-22T14:00:54.997+00:00

I did not see any dependencies with yellow cautions on them.

I already tried just unloading and even removing the UWP project. That still didn't work.

Please give more suggestions...
JarvanZhang 23,951 Reputation points

2021-10-25T06:51:28.08+00:00

Please try to empty of bin and obj folders of both the shared project and platform project. And update the VisualStudio to last stable verison for test.

Will the problem occur if you create a new project on MacOS VS2019 without installing the 3rd party library and run the project on VS? Please test to check if the problem is related to the plugin. If so, it's suggested to report the problem to it's portal.