.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?

Update: Some work is being done on the dotnet/android project that can be tracked here: dotnet/android#9455 - we will need to see if it solves the problem once released.

[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

[WilbertSuvoda]

I'm also experiencing this after a .NET 8 to .NET 9 (SDK 9.0.200) upgrade for a MAUI Blazor Hybrid app. It used to take 1-2 minutes and now it's taking about 8 minutes to build and deploy (Debug) to an Android emulator using JetBrains Rider 2024.3.6 on macOS 14.7.4 (Apple M3 Pro CPU). The build time for iOS seems faster now at least.

[bcaceiro]

It would be nice to get some feedback from the team - either acknowledgment or if there is already WIP for this

[lbulegato]

Working with Android is a nightmare:

• builds take ages
• you never know if the debug can start

iOS builds take 4 time less and it always can connect to simulator
it is no sense

[phillippschmedt]

@MartyIX hey sorry to highlight you here again. Do you know any way on how we get some attention to this issue? Thanks so much.

[davidortinau]

@phillippschmedt generate a binlog for one of your slow builds and it'll indicate where the time is being spent. If you aren't familiar with them, Copilot or ChatGPT may be able to help interpret it. Otherwise, open an issue on dotnet/android and include it so someone on the team can take a look.

[phillippschmedt]

Thank you. It looks like the issue might already exist here: dotnet/android#9455 - Will see if my binlog is slow on the same step.

[phillippschmedt]

I seems like there is some work being done on the dotnet/android project tracked here dotnet/android#9455 - not sure if this solves the issue.

[ArnabMSDN]

I think the issue is not solved yet

[ArnabMSDN]

Hi @jfversluis, just curious to know if Microsoft has provided any update on the fix?

[suugbut]

Wasting a lot of time.

========== Rebuild completed at 1:44 PM and took 07:59.812 minutes ==========

[WilbertSuvoda]

Someone on our team figured out that you can change the <EmbedAssembliesIntoApk> in the .csproj from true to false to speed up local builds significantly. Went from about 8 minutes to build to about a minute or two. I'm curious if it would work for anybody else.

[JRosanowski]

dotnet/android#9455

[uyen9vba]

I have same issue with net9.0-android35.0. For a simple app it takes 5 minutes to build!

[Sl1ghtly33]

For me the issue was that for some reason the default build configuration for MAUI is Release now. Adding -c Debug to build should help.