#elif WINDOWS doesn't work

[nk54]

Description

I want to create a service and use dependency injection.

It works on each platform except windows.
First, #elif __WINDOWS__ wasn't taken into account by Visual Studio (see screenshot below)

Next, #elif WINDOWS was recognized by Visual Studio but not by the compiler as it tells me it can't find the implementation of my service.

It should work and the documentation MUST (just my opinion, you're the boss haha) be updated to tell to developpers what's the difference between #if __ANDROID__ and #if ANDROID
On the Microsoft documentation I saw both, it's quite confusing. Even more when #if __WINDOWS__ doesn't work while #if WINDOWS does.
Edit: answer given here don't use the double underscore.

Steps to Reproduce

• create an interface inside the MAUI project
• create an implementation of that interface inside each platforms folder
• try to register the service inside MauiProgram.cs

Version with bug

Release Candidate 2 (current)

Last version that worked well

Unknown/Other

Affected platforms

Windows (I'm using Visual Studio 17.2.0 Preview 6.0)

Affected platform versions

net6.0-windows10.0.19041

Did you find any workaround?

Yes !

I handle each platform and handle WINDOWS in the #else

But it's a dirty hack because if the problem occurs on Tizen too, it cannot work

Relevant log output

No response

[Eilon]

In my experience, the underscore versions of the define's are never used. Only the "text" defines, such as #if WINDOWS, etc. There are also version-specific defines, such as WINDOWS10_0_19041_0, but those are rarely used, because most code differs only by platform, and not specific version of the platform.

Can you show a code sample that doesn't work if you use only the "text" defines?

[Eilon]

For example, with this code:

#if WINDOWS
// Windows
#elif ANDROID
// Android
#elif IOS
// iOS
#elif MACCATALYST
// MacCatalyst
#endif

I get this result, which is what I expected (note that the IOS platform is selected, and the iOS comment is "green", meaning it is included in the compilation, and all others are "grayed out"):

[jfversluis]

We're using this in various places in our own code and is described in the docs here as being #if WINDOWS.

I don't think there is an issue here. Have a look in our codebase here to see how we're using it to guide you as an example.

[nk54]

Hi @Eilon thank you for your time.

In this thread on the maui documentation, it seems we have to use #if PLATFORMNAME instead of #if __PLATFORMNAME__

If I set #if WINDOWS the compiler doesn't find my class whereas the overview of the type in Visual Studio indicates it's found on each platform

[nk54]

@jfversluis you may missed the following part

Next, #elif WINDOWS is recognized by Visual Studio but not by the compiler as it tells me it can't find the implementation of my service.

There is a bug. Don't close this yet please

[jfversluis]

As I said: we have this in multiple places in our codebase, it works fine there.

If it says that there is still something wrong, I would think it is something else. It would greatly help if you provide a reproduction sample that shows this behavior or at the very least specify what "tells me it can't find the implementation of my service." is exactly. What is the exact error message and the code that triggers it?

[nk54]

[nk54]

@jfversluis

I've written the steps : go to my message.

Add in MauiProgram this

#if ANDROID
using SimpleApp.Platforms.Android;
#elif IOS
using SimpleApp.Platforms.iOS;
#elif WINDOWS
using SimpleApp.Platforms.Windows;
#endif

Register the service

THE BUG

With #elif WINDOWS the compiler doesn't find TestService.
Replace #elif WINDOWS by #else the compiler finds the class.

It is cleaarly a bug.

The code of service if you want to repro.
// Path SimpleApp/ITestService.cs public interface ITestService { void PrintPlatform(); } // Path SimpleApp/Platforms/Windows/TestService.cs namespace SimpleApp.Windows { public class TestService : ITestService { public void PrintPlatform() => Debug.WriteLine("Windows"); } } // Path SimpleApp/Platforms/Android/TestService.cs namespace SimpleApp.Android { public class TestService : ITestService { public void PrintPlatform() => Debug.WriteLine("Android"); } } // Path SimpleApp/Platforms/iOS/TestService.cs namespace SimpleApp.iOS { public class TestService : ITestService { public void PrintPlatform() => Debug.WriteLine("iOS"); } }

[jfversluis]

This seems to work fine for me: https://github.com/jfversluis/Repro6815

Just have to make sure that either all platforms have the TestService or exclude the registration for the platforms that are not supported or remove the TargetFrameworks from the csproj that you're not going to use

[nk54]

It builds on your repro but I can't launch it.

YES ! I found the bug. @jfversluis

In your repo, create a folder Services inside Repro6815\Platforms\Windows

Move your windows implementation inside : Repro6815\Platforms\Windows\Services\SomeService.cs

Now it doesn't build anymore even if you change the namespace

[jfversluis]

That indeed seems weird!

Not to be rude here or anything just want to point it out, but I feel this would have all saved us a lot of time if there was a reproduction attached in the first place. That's why we ask for it. It can be the subtle differences.

[nk54]

Yeah I know but trust me those last few days I've been submitting severals bugs (you saw some of them)

I do what I can to help the community but i find several bugs a day on MAUI (XAML crash or weird rendering compared to the same code on Xamarin Forms) so if I spend 1 or 2 hour by bug to create the project, the repro step, to publish on github, to fill the issue here, I bet my boss would ask me to stop reporting new issues with something stupid like "other people will do it for you. Microsoft isn't the one who pays you anymore (I worked 2 years at Microsoft France) so start working for me instead of them" or he would ask me to migrate from Xamarin Forms to Flutter instead of MAUI haha.

Anyway, I'll do what I can in the future to provide a github repro project in the future ;)

I wish you a good evening!

[nk54]

LOL I didn't notice it was you @jfversluis : the famous Gerald from youtube!! 😆 I post some messages on your Youtube channel few days ago (Nicolas Krier) to say how much I love your content ;)

Glad to meet you here :D

[VincentBu]

@jfversluis, just curious, can we use the sample in #7423 to repro this issue?

[Eilon]

I was able to repro #7423 (closed as dup of this bug). I used latest VS with .NET MAUI 6 GA.

[salarcode]

Adding this to .csproj file fixes the issue for me. Looks like WINDOWS is not defined

<PropertyGroup Condition="$(TargetFramework.Contains('-windows'))">
    <DefineConstants>WINDOWS</DefineConstants>
</PropertyGroup>

[Eilon]

@salarcode yeah that's quite odd. The MAUI targets are supposed to add that automatically...

[iron4548]

@salarcode I tried your solution, but it doesn't work for me. None of the Windows platform specific methods or #if WINDOWS work for me.

Did you put that in your MAUI class library project file? Can you show us your .csproj xml file?

[iron4548]

Okay I was able to figure out why it wasn't working for me.

My solution looks like this

Console App with Target framework of NET 6.0, but Target OS is set to (None) under project settings.
.NET MAUI 6.0 class library with platform specific code, and this library is linked to the NET 6.0 Console app.

If I change my Target OS to 'Windows' for the .NET 6.0 Console App then the platform specific code in the NET 6.0 class library for Windows works.

So the solution (for now) would be to have multiple .NET 6.0 Console App projects with each project targeting a specific platform (macOS, Windows) by setting the target OS.

(The aforementioned .NET MAUI 6.0 class library is also used for a .NET MAUI App for cross-platform too)

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[MrDeej]

Hmm...

Does not work when using classes from other project of type .NET7.0

[MagicAndre1981]

this whole #if concept is crap, I liked the old XF way much more to write platform specific code.

[Eilon]

this whole #if concept is crap, I liked the old XF way much more to write platform specific code.

In .NET MAUI you can also place C# code files in "platform" folders and avoid using preprocessor directives such as #if. Learn more here: https://learn.microsoft.com/dotnet/maui/platform-integration/invoke-platform-code?view=net-maui-7.0#partial-classes-and-methods

However, I find in my own code that if I only need to special case one or two lines of code, #if is easier. I use platform folders when I have entire classes that are almost entirely different.

[MagicAndre1981]

In .NET MAUI you can also place C# code files in "platform" folders and avoid using preprocessor directives such as #if. Learn more here: https://learn.microsoft.com/dotnet/maui/platform-integration/invoke-platform-code?view=net-maui-7.0#partial-classes-and-methods

yes, I know this and already use it

However, I find in my own code that if I only need to special case one or two lines of code, #if is easier. I use platform folders when I have entire classes that are almost entirely different.

I use DeviceInfo.Current.Platform for this.

[ghost]

Hello lovely human, thank you for your comment on this issue. Because this issue has been closed for a period of time, please strongly consider opening a new issue linking to this issue instead to ensure better visibility of your comment. Thank you!