VS build Microsoft.CSharp reference conflicts and question

I've been looking for a while at posts but don't find a good answer. I'm pretty familiar with .Net and dependencies (not so much with Nuget) and all that but not sure what to do in this case. I have a Xamarin.Forms Android and iOS solution.

I have a couple reference conflicts when I build but the most glaringly obvious is between Microsoft.CSharp 2.0.5.0 and 4.0.0.0. Pasted below is the build log for this conflict.

I feel like I should have the Microsoft.CSharp.dll with a 4.0.0.0 version in, say, MonoAndroid\v9.0\Microsoft.CSharp.dll but have no idea.

I've removed and re-added various references, updated nuget packages, etc. My nuget manager says it's referencing Microsoft.CSharp 4.5.0 as does the csproj file.

Thanks.

Chris

<br /> 2> There was a conflict between "Microsoft.CSharp, Version=2.0.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" and "Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a".<br /> 2> "Microsoft.CSharp, Version=2.0.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" was chosen because it was primary and "Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" was not.<br /> 2> References which depend on "Microsoft.CSharp, Version=2.0.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" [C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\MonoAndroid\v1.0\Microsoft.CSharp.dll].<br /> 2> C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\MonoAndroid\v1.0\Microsoft.CSharp.dll<br /> 2> Project file item includes which caused reference "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\MonoAndroid\v1.0\Microsoft.CSharp.dll".<br /> 2> Microsoft.CSharp<br /> 2> References which depend on "Microsoft.CSharp, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" [].<br /> 2> C:\Users\chris\source\client\UserDetailsClient\UserDetailsClient.Core\bin\Debug\netstandard2.0\UserDetailsClient.Core.dll<br /> 2> Project file item includes which caused reference "C:\Users\chris\source\client\UserDetailsClient\UserDetailsClient.Core\bin\Debug\netstandard2.0\UserDetailsClient.Core.dll".<br /> 2> C:\Users\chris\source\client\UserDetailsClient\UserDetailsClient.Core\bin\Debug\netstandard2.0\UserDetailsClient.Core.dll<br /> 2> C:\Users\chris&#46;nuget\packages\microsoft.azure.documentdb.core\2.5.1\lib\netstandard1.6\Microsoft.Azure.DocumentDB.Core.dll<br /> 2> Project file item includes which caused reference "C:\Users\chris&#46;nuget\packages\microsoft.azure.documentdb.core\2.5.1\lib\netstandard1.6\Microsoft.Azure.DocumentDB.Core.dll".<br /> 2> C:\Users\chris&#46;nuget\packages\microsoft.azure.documentdb.core\2.5.1\lib\netstandard1.6\Microsoft.Azure.DocumentDB.Core.dll<br /> 2> C:\Users\chris\source\client\UserDetailsClient\UserDetailsClient.Core\bin\Debug\netstandard2.0\UserDetailsClient.Core.dll<br />