Documentation for Multi-Project setup. #7426

drasticactions · 2022-05-23T22:28:09Z

Description

In the MAUI GA blog entry, there is a section stating that MAUI supports being used in a "multi-project" (Multiple Projects with single target platforms, as opposed to a "Single-Project" which contains multiple target frameworks). However, I can't set it up. There's no template, nor samples in the MAUI repos for how to pull this off.

I've tried creating my own project (https://github.com/drasticactions/MauiMultiProject) to show this. While I was able to get Android to launch from a MAUI app based in a class project, I've been unable to get the others set up successfully. WinUI will throw an exception that Application.Current is null.

I'm not sure how to set this up properly. Since we say this is a supported usecase, I think there should be documentation (either a sample or a template) with it setup. That will make it easier for anyone to integrate MAUI into a "single" application project.

Steps to Reproduce

Try and run https://github.com/drasticactions/MauiMultiProject on various platforms.

Version with bug

Release Candidate 3 (current)

Last version that worked well

Release Candidate 3 (current)

Affected platforms

iOS, Android, Windows, macOS

Affected platform versions

All

Did you find any workaround?

No response

Relevant log output

No response

The text was updated successfully, but these errors were encountered:

returnZro · 2023-05-29T20:27:56Z

+1 on this. Would really appreciate some documentation. It is very difficult to maintain in a single project and most of us migrating from xamarin with an existing CI/CD environment would prefer to achieve the same project structure in MAUI as well.

Although I am able to build and run the given repo sample (with slight changes) successfully for iOS and Droid with .net7, there are still build configuration and plaform related issues especially in iOS.

As soon as I set <UseMaui> flag as true in a net7.0-ios target project, I am unable to create platforms iPhone and iPhoneSimulator under the build configuration. Explicitly setting platforms doesn't work either.

<Platforms>iPhone;iPhoneSimulator;AnyCPU</Platforms>

Shared project containing xaml views:

<TargetFramework>net7.0</TargetFramework>
<UseMaui>true</UseMaui>
<SingleProject>false</SingleProject>

iOS project:

<TargetFramework>net7.0-ios</TargetFramework>
<OutputType>Exe</OutputType>
<UseMaui>true</UseMaui>
<SingleProject>false</SingleProject>

Droid project:

<TargetFramework>net7.0-android</TargetFramework>
<OutputType>Exe</OutputType>
<UseMaui>true</UseMaui>
<SingleProject>false</SingleProject>

sam-skedulo · 2023-06-14T00:49:37Z

+1 This would greatly help the migration story since most xamarin apps are multi project setups.

Alex-Dobrynin · 2023-06-25T19:03:29Z

+1 UP

ericbrunner · 2023-06-26T08:40:33Z

++ 1 UP Hey @jfversluis Why is there no response on that issue? We want to keep the Xamarin.Forms architecture as Multi-project solution, even after migration to MAUI.

jfversluis · 2023-06-26T09:44:41Z

@ericbrunner if that is what you want, you should be able to use the .NET Upgrade Assistant which will help you with both that migration as well as doing that with multiple projects.

Haukinger · 2023-06-26T09:51:40Z

+1 UP please document creating multi-project setup for new apps, too, not only migrating old ones

ericbrunner · 2023-06-26T10:27:08Z

@jfversluis if it would be that easy I would'nt bother you. I tried CLI ugrade-assistant and converted android, ios and the common xamarin project but did't get it working. Now I try the VS Ugrade Tool extension and the latest VS Preview version

jfversluis · 2023-06-26T11:42:50Z

I've just tried the repo in the first comment (https://github.com/drasticactions/MauiMultiProject) and without changing anything I was able to run iOS, Android and Mac Catalyst. So you basically want to mimic whatever is in that project.

For Windows there seems to be something not working unfortunately, probably because some configuration is missing or incomplete.

I understand this issue is about documentation for it, I don't think that will come anytime soon. Single-project is our recommended and primary approach at this time. Maybe someone from the community might be able to help out here.

ericbrunner · 2023-06-26T12:14:08Z

@jfversluis interesting. I have no devices to choose from im visual studio for that (https://github.com/drasticactions/MauiMultiProject).
dispite the fact that one real and on emulator device are avialable (see vysor on left side)

therefore that error message

jfversluis · 2023-06-26T13:31:51Z

Interesting. I was on Visual Studio for Mac and it worked without a problem there. On Windows I indeed see the same. Ironically enough, adding <SingleProject>True</SingleProject> to your Android project makes the devices show up.

Then it complains about some resources it can't find in the AndroidManifest.xml. Seems like that happens because the files under Resources aren't set to BuildAction AndroidResource.

mattleibow · 2023-06-27T03:34:30Z

SingleProject=True tells the compiler that the root things are shared and it needs to look at Platforms/Android

The IDE not showing devices is a separate bug and should be logged with VS using the feedback tool.

mattleibow · 2023-06-27T03:35:25Z

@jfversluis what is the error for windows?

mattleibow · 2023-06-27T03:37:00Z

@davidbritch do we have docs for multiple projects? Do we need docs or does/should it just work? Is there any docs with the upgrade assistant maybe?

jfversluis · 2023-06-27T12:09:20Z

Then it complains about some resources it can't find in the AndroidManifest.xml. Seems like that happens because the files under Resources aren't set to BuildAction AndroidResource.

This is what I meant by

Then it complains about some resources it can't find in the AndroidManifest.xml. Seems like that happens because the files under Resources aren't set to BuildAction AndroidResource.

Remove the references to those files or (probably) set the BuildAction for those files to AndroidResource

jfversluis · 2023-06-27T12:09:45Z

@davidbritch do we have docs for multiple projects? Do we need docs or does/should it just work? Is there any docs with the upgrade assistant maybe?

@davidortinau I think this is more upgrade related, I think that was on your plate?

jfversluis · 2023-06-27T12:16:50Z

@jfversluis what is the error for windows?

@mattleibow It's hard to capture the details, but I think the key is somewhere here.

It throws an NRE and if you look at the Stack Trace, it just calls the InitializeComponent and goes through XAML stuff, but there is a hint to a RadioButton there (there is no RadioButton in the app...) and some reference to ResolveThemeColor.

My gut tells me there is some initialization somewhere that is missed.

Full call stack: https://gist.github.com/jfversluis/ab3b01d7fb570ec0025a578e5969aa89

ericbrunner · 2023-06-27T12:49:01Z

If someone interested, here is an original Xamarin.Forms solution and a Migration to a MAUI Single-Project and Multi-Project Solution:

Xamarin.Forms Original Codebase: https://github.com/ericbrunner/TaskyApp.XamarinForms.git
.NET MAUI Migration as Single-Project Codebase: https://github.com/ericbrunner/TaskyApp.Maui.SingleProject.git
.NET MAUI Migration as Multi-Project Codebase: https://github.com/ericbrunner/TaskyApp.Maui.git => @jfversluis it would be nice when you can take a look on the iOS project in the Multi-Project. When I start the app the iOS screen remains black. Android is working.

ericbrunner · 2023-06-28T04:53:00Z

Resources aren't set to BuildAction AndroidResource.

@jfversluis You comment your own comment. Pretty awesome ;-) Ok, let's get more serious.

I had success with the AndroidResources in a Multi-Project Solution. But it's not fully as you explained.

The mipmap/icon compiler error could be fixed by right-click on

and set to AndroidResource.
My Drawable icons where not accessible dispite that I set all Drawable Android images to AndroidReosurce.

After some investigation I found @mattleibow reported an issue Not easy to add a "AndroidResource" to a maui project and Resource is ambiguous.

So the trick is to fully qualify your Resource in the Android Project, because one is the MAUI Resource and one is the Android Platform Resource. So you end up with to different created Resource.designer.cs.

yevgeny-sotnikov · 2023-07-10T23:22:18Z

+1UP

Alvin-2101 · 2023-09-22T21:31:04Z

If someone interested, here is an original Xamarin.Forms solution and a Migration to a MAUI Single-Project and Multi-Project Solution:

Xamarin.Forms Original Codebase: https://github.com/ericbrunner/TaskyApp.XamarinForms.git

.NET MAUI Migration as Single-Project Codebase: https://github.com/ericbrunner/TaskyApp.Maui.SingleProject.git

.NET MAUI Migration as Multi-Project Codebase: https://github.com/ericbrunner/TaskyApp.Maui.git => @jfversluis it would be nice when you can take a look on the iOS project in the Multi-Project. When I start the app the iOS screen remains black. Android is working.

Multi-Project is not available through the given link, can you please share it again.

ericbrunner · 2023-09-23T08:25:41Z

@Alvin-2101 Multi-Project was cancelled on my side due to the Microsoft advice to work with a Single-Project structure

ericbrunner · 2023-09-23T08:37:42Z

@Alvin-2101 I added a Migration Guide here, maybe helpful.

Alvin-2101 · 2023-09-23T08:43:43Z

@Alvin-2101 I added a Migration Guide here, maybe helpful.

Thanks I will take a look.

mattleibow · 2023-09-23T16:23:34Z

I also created a multi head maui app project and template some time ago https://github.com/mattleibow/MauiMultiHeadProject

Rickvanderwaal · 2023-09-25T13:01:18Z

@jfversluis interesting. I have no devices to choose from im visual studio for that (https://github.com/drasticactions/MauiMultiProject). dispite the fact that one real and on emulator device are avialable (see vysor on left side) therefore that error message

I'm experiencing the same issues. In Visual Studio no devices to select. When pressed Start i always get some Android simulator. Any solutions to this?

jameslavery · 2023-10-05T11:20:29Z

@Alvin-2101 Multi-Project was cancelled on my side due to the Microsoft advice to work with a Single-Project structure

So does this mean that Microsoft aren't supporting Multi-Project now? I can't find any up to date recommendations or un-recommendations.

I'm looking at upgrading a pretty complex existing application, which I think would be better kept as multi-project. But I don't want to find that I've got problems later on. This is the flagship app for my client, and it would be disastrous to pick the wrong structure and have errors/problems as a result.

Alvin-2101 · 2023-10-05T12:32:59Z

I am keeping the multiple structure until the point I can and then I will be moving to a single project structure.

jameslavery · 2023-10-05T12:44:31Z

I am keeping the multiple structure until the point I can and then I will be moving to a single project structure.

Thanks -I think I need to take the plunge and go for the probably more complex migration and go straight to single project.

trampster · 2023-10-09T20:20:34Z

We just tried to migrate to a large Xamarin.Forms app to a multi project solution, we ran into this problem of not being able to deploy.

If Microsoft isn't going to support/fix the multi project solution then they should remove it from the migration guide and make it obvious that you have to go straight to a single project solution.

returnZro · 2023-10-09T20:25:38Z

We just tried to migrate to a large Xamarin.Forms app to a multi project solution, we ran into this problem of not being able to deploy.

If Microsoft isn't going to support/fix the multi project solution then they should remove it from the migration guide and make it obvious that you have to go straight to a single project solution.

Can you elaborate on what exactly is the problem/error that you are facing and for which platform?

trampster · 2023-10-09T20:38:52Z

Same as the people above. There is no deploy option. The green play button just says "Start" the drop down doesn't have the options for android Emulators or Android Local Devices. If you do click on "Start" it fails on the deploy stage but with no info about why (not surprising since I couldn't select where to deploy to)

This is the same as reported by people above, and the consensus seems that you have to use single project solution for it to work. There is no sample for multiple project solutions, there is no dotnet new support, there is no Visual studio new project option. And the Microsoft employee who made an example above (but couldn't get it working) deleted it because he was told to only focus on the single project solution.

Our app supports Android and iOS but we have only migrated android so far.

yevgeny-sotnikov · 2023-12-23T13:21:46Z

I also created a multi head maui app project and template some time ago https://github.com/mattleibow/MauiMultiHeadProject

Hi @mattleibow, thank you for this template, it's helpful for our migration. But i have a question: how do we need to declare MAUI Handlers at such project structure? Thank you in advance

returnZro · 2023-12-28T21:37:15Z

I also created a multi head maui app project and template some time ago https://github.com/mattleibow/MauiMultiHeadProject

Hi @mattleibow, thank you for this template, it's helpful for our migration. But i have a question: how do we need to declare MAUI Handlers at such project structure? Thank you in advance

I don't know if there is any recommended way from MS for this but this is how I register the handlers:

I have MauiProgram.cs in my shared project. The CreateMauiApp function is set to accept MauiAppBuilder as a parameter.

public static MauiApp CreateMauiApp(MauiAppBuilder builder)
{
        builder
            .UseMauiApp<App>();

        return builder.Build();
}

Then in platform projects, in AppDelegate.cs, override the CreateMauiApp function, create a builder, register the iOS specific handler and pass the builder to MauiProgram.CreateMauiApp.

Do the same for Droid in MainApplication.cs

protected override MauiApp CreateMauiApp()
{
        var builder = MauiApp.CreateBuilder();

        // register your platform handlers to builder here

        return MauiProgram.CreateMauiApp(builder);
}

mattleibow · 2024-02-15T17:02:09Z

Adding an official template here: #20365

yevgeny-sotnikov · 2024-09-20T16:02:13Z

@mattleibow One new question - how to build and run only one platform in Muliti-Project structure?

My case is - i have very limited space for Windows environment and I installed only MAUI & WinUI3 SDK. I don't need to install more SDKs cuz I'm going to test only Windows part, but VS is continiosly asking about Android, iOS and Mac SDK and plcks ability to build WinUI3 project only

Issue is only happening on Windows at VisualcStudio, neither VS4Mac nor rider has this issue. Thank you for your answer in advance

drasticactions added the area-docs Conceptual docs, API docs, Samples label May 23, 2022

drasticactions changed the title ~~Can't create Multi-Project Setup.~~ Documentation for Multi-Project setup. May 23, 2022

drasticactions assigned mattleibow May 24, 2022

samhouts added the partner Issue or Request from a partner team label Jul 20, 2022

mattleibow removed their assignment Aug 3, 2022

mattleibow added this to the Backlog milestone Aug 3, 2022

samhouts added the Task neither bug nor feature but something that needs to be done in support of either label Jul 31, 2023

rachelkang added the migration-compatibility Xamarin.Forms to .NET MAUI Migration, Upgrade Assistant, Try-Convert label Jan 25, 2024

samhouts added platform/macOS 🍏 macOS / Mac Catalyst platform/windows 🪟 platform/android 🤖 platform/iOS 🍎 labels Feb 2, 2024

github-actions bot mentioned this issue Jun 13, 2024

Multiple project templates. The project file is being loaded all the time. You need to reopen the solution in order to work properly. #23040

Closed

Documentation for Multi-Project setup. #7426

Documentation for Multi-Project setup. #7426

Comments

drasticactions commented May 23, 2022

Description

Steps to Reproduce

Version with bug

Last version that worked well

Affected platforms

Affected platform versions

Did you find any workaround?

Relevant log output

returnZro commented May 29, 2023

sam-skedulo commented Jun 14, 2023

Alex-Dobrynin commented Jun 25, 2023

ericbrunner commented Jun 26, 2023 • edited Loading

jfversluis commented Jun 26, 2023

Haukinger commented Jun 26, 2023

ericbrunner commented Jun 26, 2023

jfversluis commented Jun 26, 2023

ericbrunner commented Jun 26, 2023 • edited Loading

jfversluis commented Jun 26, 2023 • edited Loading

mattleibow commented Jun 27, 2023

mattleibow commented Jun 27, 2023

mattleibow commented Jun 27, 2023

jfversluis commented Jun 27, 2023

jfversluis commented Jun 27, 2023

jfversluis commented Jun 27, 2023 • edited Loading

ericbrunner commented Jun 27, 2023 • edited Loading

ericbrunner commented Jun 28, 2023 • edited Loading

yevgeny-sotnikov commented Jul 10, 2023

Alvin-2101 commented Sep 22, 2023

ericbrunner commented Sep 23, 2023 • edited Loading

ericbrunner commented Sep 23, 2023

Alvin-2101 commented Sep 23, 2023

mattleibow commented Sep 23, 2023

Rickvanderwaal commented Sep 25, 2023 • edited Loading

jameslavery commented Oct 5, 2023

Alvin-2101 commented Oct 5, 2023

jameslavery commented Oct 5, 2023

trampster commented Oct 9, 2023 • edited Loading

returnZro commented Oct 9, 2023

trampster commented Oct 9, 2023 • edited Loading

yevgeny-sotnikov commented Dec 23, 2023

returnZro commented Dec 28, 2023

mattleibow commented Feb 15, 2024

yevgeny-sotnikov commented Sep 20, 2024 • edited Loading

ericbrunner commented Jun 26, 2023 •

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ericbrunner commented Jun 26, 2023 •

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jfversluis commented Jun 26, 2023 •

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jfversluis commented Jun 27, 2023 •

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ericbrunner commented Jun 27, 2023 •

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ericbrunner commented Jun 28, 2023 •

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ericbrunner commented Sep 23, 2023 •

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Rickvanderwaal commented Sep 25, 2023 •

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trampster commented Oct 9, 2023 •

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trampster commented Oct 9, 2023 •

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yevgeny-sotnikov commented Sep 20, 2024 •

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