After updating to Visual Studio Mac to the latest Platforms property is not working.

Julian Dormon 6

After updating to Visual Studio for Mac 17.4, when doing a brand new Maui Blazor app, the Platforms property is broken.

The platforms folder is where it ought to be.

And what's strange, is that I have an older Maui app which uses the same code and it does not encounter this error running in the same version of Visual Studio.
So something has changed in the Configuration when setting up a new project.

Version info moved from where it was a posted as an answer:

Visual Studio Community 2022 for Mac Preview
Version 17.4 Preview (17.4 build 1583)
Installation UUID: 10e52aa0-ff80-4b74-8350-1c794fdcca3c

Runtime
.NET 6.0.5 (64-bit)
Architecture: Arm64

Roslyn (Language Service)
4.4.0-2.22419.1+ae5663806be933515723b2d5a85faf5d378f460d

NuGet
Version: 6.3.0.128

.NET SDK (Arm64)
SDK: /usr/local/share/dotnet/sdk/6.0.401/Sdks
SDK Versions:
6.0.401
6.0.400
6.0.400-preview.22330.6
MSBuild SDKs: /Applications/Visual Studio (Preview).app/Contents/MonoBundle/MSBuild/Current/bin/Sdks

.NET SDK (x64)
SDK Versions:
5.0.408
3.1.423
3.1.422
3.1.421

.NET Runtime (Arm64)
Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
6.0.9
6.0.8
6.0.6

.NET Runtime (x64)
Runtime: /usr/local/share/dotnet/x64/dotnet
Runtime Versions:
5.0.17
3.1.29
3.1.28
3.1.27

Xamarin.Profiler
Version: 1.8.0.19
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

Updater
Version: 11

Apple Developer Tools
Xcode 14.0 (21335)
Build 14A400

Xamarin.Mac
Version: 8.12.0.2 (Visual Studio Community)
Hash: 87f98a75e
Branch: d17-3
Build date: 2022-07-25 20:18:54-0400

Xamarin.iOS
Version: 15.12.0.2 (Visual Studio Community)
Hash: 87f98a75e
Branch: d17-3
Build date: 2022-07-25 20:18:55-0400

Xamarin Designer
Version: 17.4.0.124
Hash: ffbba0c031
Branch: remotes/origin/d17-4
Build date: 2022-09-15 15:36:42 UTC

Xamarin.Android
Version: 13.0.99.81 (Visual Studio Community)
Commit: xamarin-android/main/7c9c24b
Android SDK: /Users/macminim1/Library/Developer/Xamarin/android-sdk-macosx
Supported Android versions:
12.0 (API level 31)

SDK Command-line Tools Version: 7.0
SDK Platform Tools Version: 33.0.2
SDK Build Tools Version: 33.0.0

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 26,146 Reputation points Microsoft Vendor

2022-09-19T07:04:58.223+00:00

Could you provide the detailed error message? As noted in the Q&A FAQ: How to write a quality question
You could try to enter the full namespace ( FaceRecognition1.Platforms ). From the image, the target is .net android, you could try to select .net maccatalyst, and check if the error still exists.
Julian Dormon 6 Reputation points

2022-09-19T13:59:37.663+00:00

The type or namespace name "Platforms" could not be found. Are you missing an assembly or reference...
Julian Dormon 6 Reputation points

2022-09-19T14:04:33.367+00:00

I tried your suggestion but still the problem persists.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 26,146 Reputation points Microsoft Vendor

2022-09-20T09:19:07.373+00:00

I tried to created a new interface( IFolderPicker ) and implement the interface( FolderPicker ) under Platforms/MacCatalyst. It works with Visual Studio for Mac 17.4, I can't reproduce this issue. Would you mind sharing some code snippets about your IFolderPicker and FolderPicker so that I can test? Does this error still exist when you create a new empty MAUI Blazor project and add the picker? And could you provide the detailed environment information such as the .net version?
Rob Caplan - MSFT 5,412 Reputation points Microsoft Employee

2022-09-27T19:48:03.89+00:00

I copied the version info you provided into the main question. That's a better place for essential information than in a comment or an answer.

Note that MAUI itself doesn't contain a Platforms property. I suspect your original project was based on a sample which included code in a Platforms namespace, so if you created a new project you would need to include the code from the sample to use it.