.NET 9 Android: Very slow build times

[phillippschmedt]

When upgrading our project from .NET 8 to .NET 9 the build times on local debug massively increased. It's easily 4x-5x slower making working with Android a pain. Also after the long build the app will often not start on the device and I need to start a 10 minutes build again.

Anyone else noticed this? Any ideas how to fix it?

[voroninp]

For me it is also frequent "Waiting for Debugger to Attach" and freezed VS when breakpoint is hit. ='(

[ArnabMSDN]

I am experiencing frequent issues with the Android Emulator while working with .NET MAUI. The emulator often stops working and gets stuck on "Waiting for Debugger to Attach." Even after resetting the emulator and applying the suggested fixes, the issue persists, making development highly frustrating. The time spent troubleshooting emulator problems significantly impacts productivity. I would like to request Microsoft to investigate and provide a more stable solution for the emulator to ensure a smoother development experience.

https://learn.microsoft.com/en-us/answers/questions/2151565/unable-to-start-net-maui-application-on-android-em

[phillippschmedt]

Anything we can do here? Working with Android is impossible right now. Build times are like 10 minutes in debug and then the build often won't start on the device. This is huge problem for us. Who can help here?

[phillippschmedt]

@davidortinau I want to bring this to your attention. Is there anything you can provide here on how to solve the long build times?

[stephenquan]

Are you building with dotnet build command line or in Visual Studio? Because if it's the command line, as of .NET 9 there seems to be a change with the implicit build configuration. It appears to have changed from -c Debug to -c Release. This was one of the biggest changes we observed in our CI/CD. To get faster debug builds in our CI/CD we need to explicitly set the -c Debug configuration.

[phillippschmedt]

Thank you. I am working with rider and it's setting -c Debug. Our release builds are even slower, because of the AOT compilation.

[MartyIX]

Perhaps @jonathanpeppers would know.

[bcaceiro]

Well, in Visual studio windows, it is building iOS, Windows, even if you target Android. Which will make things even slower.
But yeah, long build times.

[phillippschmedt]

I noticed that before too. During an Android build it executes a lot of iOS related commands.

[JoeVoo]

I am realizing an improvement in Net9's start times, both in Windows and Android. In the already open Android emulator, I see the logo after 16 seconds and the start page after 26 seconds when making one change on a C# page. Start with IDE, Hotreload on.
On my old Iphone 7, i can not debug because starting runs into apple timeout (no changes since Net6). Emulators start fast.

When i first tested Net9 in November, i had more than 500 Warnings so i decided to return to Net8. Now, with no Xaml pages left, i decided to switch to Net9 again and it works well.

I use MVVM but not the MVVM Toolkit.
I have Maui toolkit, syncfusion, efc
I have 11 projects in the solution.
I have only a small number of source generated files (10).
I have 60 pages but no XAML page left. I have XAML Styles.

The release build needs more than 7 minutes. That is indeed too long. One should actually test the release more often because you can't rely on it behaving like the debug version. I do this far too seldom, perhaps once a month. I should do it daily.

In the past, when i had slow start times, i found a too old license key for the syncfusion controls.

I would check your Nugets for problems.

[phillippschmedt]

Thanks for sharing your experience. This discussion is mainly about build times, not startup times. Once the app is build the start of the app happens in a reasonable amount of time.

[JoeVoo]

Ok, no problem. My understanding was the start time after changing something (F5). I thought this is relevant for working (with debugger).

Build with F6 is indeed slower, but this is the same for all platforms because it builds all platforms.
Windows, Ios, Android, Mac

My App build time after one change in code (F6):
Net8: 0:45, Net9 1:08

Complete rebuild Solution in debug
Net8: 1:52, Net9: 2:32

Complete Build Main App in Release:
Net8: not checked, Net9: 7:41
.....
12>[301/303] Mono.Android.Runtime.dll -> Mono.Android.Runtime.dll.so
12>[302/303] Mono.Android.dll -> Mono.Android.dll.so
12>[303/303] System.Private.CoreLib.dll -> System.Private.CoreLib.dll.so
========== Build: 12 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========
========== Build completed at 14:06 and took 07:41,573 minutes ==========

CPU not very fast, 100% all the time, 32GB Ram