Is an iOS Framework .NET Binding Library in MAUI Possible?

Question

I am attempting to update a project from Xamarin.Forms to Maui, that uses a binding project to wrap an iOS .framework library. I am not able to reference my Xamarin iOS Binding library in the Maui App; I need to create a new iOS Binding Library that targets .NET 6 iOS. I have been having trouble referencing the iOS Binding Library from the Maui App.

I have created a minimal Objective-C Framework, and validated it by integrating it into a Xamarin binding project and Xamarin.Forms project, and it works as expected - I am able to call into the Objective-C iOS Framework code from the application C# code.

But, when I try to consume a .NET 6 iOS Binding Library that uses the same Objective-C iOS Framework, I am lost. Visual Studio 17.3.0 preview allows me to create an iOS Binding Library, but it does not allow me to add a Native Framework Reference (the project context UI exists but is a no-op when I click it). So, I have manually modifed the iOSBinding .csproj file to reference the iOS Framework similarly to how the Xamarin binding library (from attached 210383-testmauiframeworkbindingscsproj.txt):

<ItemGroup>  
<NativeReference Include="Native References/TestFramework.framework">  
<Kind>Framework</Kind>  
</NativeReference>  
</ItemGroup>  

This seems to work, in that I can (supposedly) successfully build this iOSBinding project But, I get linker errors when I try to build the Maui App. The Maui App references the iOSBinding project via (from attached 210309-testmauiappcsproj.txt):

<ProjectReference Include="..\TestMauiFrameworkBindings\TestMauiFrameworkBindings.csproj" />  

When I build the Maui App I get the following build errors (from attached 210310-build.log):

--------------

1>C:\Program Files\dotnet\packs\Microsoft.iOS.Windows.Sdk\15.4.303\tools\msbuild\iOS\Xamarin.iOS.Common.After.targets(327,3): warning MT1302: Could not extract the native library 'TestFramework.framework' from '/Users/r_dsdcompb/Library/Caches/Xamarin/mtbs/builds/TestMauiApp/694bb3adfa58e8cc00b59acf89a20a0c002608c09695ad5f70b5d9442fc8a3d7/obj/Debug/net6.0-ios/ios-arm64/linker-cache/TestFramework.framework.zip'. Please ensure the native library was properly embedded in the managed assembly (if the assembly was built using a binding project, the native library must be included in the project, and its Build Action must be 'ObjcBindingNativeLibrary').

...

1>C:\Program Files\dotnet\packs\Microsoft.iOS.Windows.Sdk\15.4.303\tools\msbuild\iOS\Xamarin.iOS.Common.After.targets(327,3): error MT0140: File '/Users/r_dsdcompb/Library/Caches/Xamarin/mtbs/builds/TestMauiApp/694bb3adfa58e8cc00b59acf89a20a0c002608c09695ad5f70b5d9442fc8a3d7/obj/Debug/net6.0-ios/ios-arm64/linker-cache/TestFramework.framework/TestFramework' is not a valid framework.
1>

...

1>C:\Program Files\dotnet\packs\Microsoft.iOS.Windows.Sdk\15.4.303\tools\msbuild\iOS\Xamarin.iOS.Common.After.targets(368,3): error MSB3371: The file "obj\Debug\net6.0-ios\ios-arm64\linked\Link.semaphore" cannot be created. Could not find a part of the path 'C:\Users\R_DSLC\source\FrameworkTest_ForGithub\TestMauiApp\TestMauiApp\obj\Debug\net6.0-ios\ios-arm64\linked\Link.semaphore'.

--------------

I am not sure how to move forward. I'm not able to use the 'ObjcBindingNativeLibrary' Build Action for the framework as it doesn't even show up in VS. If I attempt to make the NativeReference xml element ObjcBindingNativeLibrary, I get a 'access to ... TestFrameworkFolder is denied'. I've attempting disabling linking and many other csproj shenanigans... If I end up circumventing the linker error, I get a runtime error that the .dll is not able to be loaded (it isn't packaged).

Has anyone successfully linked and used an iOS Binding Project that uses a native iOS framework? I'm assuming this is possible but I'm missing some detail in either my binding or app .csproj files.

Thanks for reading!

Answer 1

@Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) I can't find any answers in the the other links you provided above for other similar reported questions, nothing is helpful there.
Can someone please create a binding library that uses .framework and NOT ".a" static lib along with working MAUI demo that uses the binding library so we can close this issue and get it over with? you guys keeps directing us from one link to another with nothing helpful.

A fully working binding library and MAUI demo that uses it will be much helpful, is that possible?
Again, we need to use .framework and NOT iOS static lib "*.a".