'Platform' does not contain a definition for 'Init' (iOS) about maui HOT 4 OPEN

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Closed similar issues:

• 'Platform' does not contain a definition for 'Init' (#21253), similarity score: 0.87
• Another - Error CS0246: The type or namespace name 'MauiUIApplicationDelegate' could not be found (are you missing a using directive or an assembly reference?) (CS0246) (#21751), similarity score: 0.77
• .NET 8 - No reference to MauiUIApplicationDelegate and ViewRenderer<,> (#18795), similarity score: 0.76
• The type or namespace name 'MauiUIApplicationDelegate' could not be found Microsoft.AspNetCore.Components.WebView.Maui 8.0.7 (#20591), similarity score: 0.75
• error CS0234: The type or namespace name 'iOS' does not exist in the namespace 'Microsoft.Maui.Controls.Compatibility.Platform' (#20589), similarity score: 0.74

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from maui.

Added repro repo (tho it was created with just the 3 steps listed above)

from maui.

Yeah, your repro shows this working.

My guess, based on your error, is that you either have that code inside a file that is being referenced by another target framework. Even though you mentioned this happening in AppDelegate in (I think) a MAUI UI project, which I also tried and worked fine, as expected.

This would only works on iOS/Catalyst, and the single target MAUI solution targets iOS, Catalyst, Windows, and Android. So maybe you have it placed somewhere we're it's trying to be compiled for other platforms. Or maybe your IDE is targeting that file for other platforms and it's showing it as failing, but it would compile fine from CLI. My guess looking at that other issue you linked to is they had the same issue. Without having a sample project nor context into where they were typing their code, it was probably targeting the base TFM where nothing exists for Platform.

There is no change in that API from net7.0 to net8.0. IMO I don't think there's a bug here, I think it's more a configuration issue with your project and/or IDE. Could you try creating a MAUI UI project showing your issue?

from maui.

Ok, I had to do 2 things:

• Upon updating Visual Studio, it fixed it in the repro project. But it still occurred in my actual app.
• I had to change the Target OS version of the project to 17.2. Anything lower than that (even 17.0) causes this to occur, including in the sample project.

When the issue is present, if I go to the definition of Microsoft.Maui.ApplicationModel, I can see that it's because the #elif IOS || MACCATALYST case isn't being compiled. aka IOS isn't defined. I'm not sure why it should be necessary to both upgrade Visual Studio and change the target OS version for that to be defined, but in any event, it is an extremely unclear error that seems to crop up on multiple platforms, so it seems like there'd be a better way to handle it / report the issue to the user...?

from maui.