LayoutBindings: 'PreserveAttribute' is obsolete warnings

Android application type

Android for .NET (net6.0-android, etc.)

Affected platform version

VS2022 17.3.6

Description

We are using a lot of AndroidBoundLayout in our app but this results in 2 warnings per layout file:

warning CS0618: 'PreserveAttribute' is obsolete: 'Please use [System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute]'

[global::Android.Runtime.PreserveAttribute (Conditional=true)]
public AboutSequriX (
	global::Android.App.Activity client,
	global::Xamarin.Android.Design.OnLayoutItemNotFoundHandler itemNotFoundHandler = null)
		: base (client, itemNotFoundHandler)
{}

[global::Android.Runtime.PreserveAttribute (Conditional=true)]
public AboutSequriX (
	global::Android.Views.View client,
	global::Xamarin.Android.Design.OnLayoutItemNotFoundHandler itemNotFoundHandler = null)
		: base (client, itemNotFoundHandler)
{}

We would like to get to 0 build warnings :)

Steps to Reproduce

Did you find any workaround?

No response

Relevant log output

No response

Those look like they are coming from the Xamarin.Android.Support.Design Nuget Package.
I believe the recomendation now is to upgrade to use AndroidX rather than the old packages.
So you will need to migrate the code away from the old Support libraries to AndroidX.

See https://learn.microsoft.com/en-us/xamarin/android/platform/androidx for more details.

The PreserveAttribute is going to be removed in a future version of .net so migrating is the best option.

@dellis1972

@dellis1972 I don't have any nuget packages Xamarin.Android.Support or any referencing it. Only AndroidX.

Example project. I created a new .NET 6 Android project, changed activity_main.xml to AndroidBoundlayout and added an ID.
AndroidApp2.zip

1>C:\git\AndroidApp2\AndroidApp2\obj\Debug\net6.0-android\generated\Binding.activity_main.g.cs(12,4,12,45): warning CS0618: 'PreserveAttribute' is obsolete: 'Please use [System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute]'
1>C:\git\AndroidApp2\AndroidApp2\obj\Debug\net6.0-android\generated\Binding.activity_main.g.cs(19,4,19,45): warning CS0618: 'PreserveAttribute' is obsolete: 'Please use [System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute]'

Ah. Are you using LayoutBindings?

Ignore that, yes you are :) sorry.

OK, that is where the issue is then.

I would guess that there would need to be an if added to support both classic with PreserveAttribute and .NET 6 with DynamicDependencyAttribute.
https://github.com/xamarin/xamarin-android/blob/ab6712a48e4b93e9c3d605c7b393814d477e2bc8/src/Xamarin.Android.Build.Tasks/Tasks/GenerateLayoutBindings.CSharpBindingGenerator.cs#L221

A additional property would be probably be needed to feed the MsBuild task, perhaps UsingAndroidNETSdk?
https://github.com/xamarin/xamarin-android/blob/ab6712a48e4b93e9c3d605c7b393814d477e2bc8/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets#L1152

DynamicDependencyAttribute works in the reverse manner to the old PreserveAttribute. The old system you placed the attribute at the code you wanted to preserver. The new DynamicDependencyAttribute you have to place it where the type is consumed. So we need to figure out the best way to deal with this without requiring the user to add the DynamicDependencyAttribute to the activity where its used.

Is the attribute even needed? This is the C# binding which is used by the developer so if unused constructors are removed it shouldn't be a problem?

The file should also contain the autogenerated comment so any warnings would be ignored.

The file should also contain the autogenerated comment so any warnings would be ignored.

A little more information on that:

[generator] Mark generated .cs files as such so Roslyn analyzers can choose to ignore them. java-interop#1052.
Generated files (e.g, Java.Interop.__TypeRegistrations.cs) should mark themselves as auto-generated java-interop#1051 (comment)

I'm still seeing this issue in NET 7 Android 33, even though #1051 is resolved.

There is no autogenerated comment in generated/Binding.xxx.g.cs

This change was too late to make it into .NET 7, I would suspect that it is fixed in .NET 8 Previews.

Same issue in .NET 8.
xxxx\obj\Debug\net8.0-android\codebehind\Binding.StartWorkShift.g.cs(19,4,19,45): warning CS0618: 'PreserveAttribute' is obsolete: 'Please use [System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute]'

[LayoutBindings] LayoutBindings: 'PreserveAttribute' is obsolete warn…

Would it be possible to backport to .NET 8 if it's a limited change: only adding <auto-generated> comment?

Yes, we can consider taking this one to .NET 8 servicing after it's merged:

[LayoutBindings] LayoutBindings: 'PreserveAttribute' is obsolete warnings #8529

[LayoutBindings] LayoutBindings: 'PreserveAttribute' is obsolete warn…

[LayoutBindings] Fix '[Preserve]' is obsolete warnings (#8529)

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LayoutBindings: 'PreserveAttribute' is obsolete warnings #7480

Android application type

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LayoutBindings: 'PreserveAttribute' is obsolete warnings #7480

Description

Android application type

Affected platform version

Description

Steps to Reproduce

Did you find any workaround?

Relevant log output

Activity

dellis1972 commented on Oct 21, 2022

rgroenewoudt commented on Oct 21, 2022

dellis1972 commented on Oct 21, 2022

dellis1972 commented on Oct 21, 2022

rgroenewoudt commented on Oct 26, 2022

dellis1972 commented on Oct 26, 2022

rgroenewoudt commented on Oct 27, 2022

jpobst commented on Nov 28, 2022

rgroenewoudt commented on Mar 13, 2023

jpobst commented on Mar 13, 2023

rgroenewoudt commented on Nov 23, 2023

rgroenewoudt commented on Dec 21, 2023

jonathanpeppers commented on Jan 3, 2024

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