How to use a (.a) Library in a .NET Maui iOS project

Wael Bouchnak 31

I was able to use a (.a) library from my xamarin project.

i used to add my library this way in the iOS project .csproj

  <ItemGroup>
    <NativeReference Include="Native References/MyLib.a">
      <Kind>Static</Kind>
      <ForceLoad>True</ForceLoad>
      <IsCxx>True</IsCxx>
      <SmartLink>True</SmartLink>
    </NativeReference>
  </ItemGroup>

in my Xamarin Project, every thing works fine :)

i tried to migrate the project to MAUI, I added the same functions, wrappers in my .NET Maui project... and i was not able to call the library

i tried first to add the same (.a) library in .csproj in this way ( Does not work )

	<ItemGroup>	  
    <NativeReference Include="Platforms\iOS\libs\MyLib.a">
      <Kind>Static</Kind>
      <ForceLoad>True</ForceLoad>
      <IsCxx>True</IsCxx>
      <SmartLink>True</SmartLink>
    </NativeReference>
  </ItemGroup>

then i tried this ( also does not work )

	<ItemGroup>	  
    <ObjBindingNativeLibrary Include="Platforms\iOS\libs\MyLib.a">
    </ObjBindingNativeLibrary>
  </ItemGroup>

i don't find any documentation about this in microsoft Maui docs

is there any project or any sample or any docs about this ???

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,841 Reputation points Microsoft Vendor

2023-03-17T08:52:02.4466667+00:00

You mean reference Native Libraries in Xamarin.iOS and you want to do the same thing with MAUI, right? Or you created an iOS binding project then add .a file to this binding project? Can you link this iOS library to a dotnet- iOS project(without MAUI)?
Wael Bouchnak 31 Reputation points

2023-03-17T09:14:56.19+00:00

@Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.)

I built a fat iOS C++ library (.a) and was able to call its functions from my xamarin Project directly.

The problem is in my Maui project, i'm not able to call it, there is no documentation about it in Maui Docs.

1/ I tried to add the Library directly in my Maui Project in "Platforms\iOS\myLib.a" ( does not work )

2 / then I Added the (.a) lib in a dotnet-iOS project in "Native References" and referenced the dotnet-iOS project in my Maui project and tried to call it the lib functions, always library not found ( "System.DllNotFoundException has been thrown __Internal" )
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,841 Reputation points Microsoft Vendor

2023-03-20T06:26:58.5533333+00:00

You reference location is "Platforms\iOS\libs\MyLib.a", but the library is in "Platforms\iOS\myLib.a", you can try to create a libs folder and check if this error still exists.
Wael Bouchnak 31 Reputation points

2023-03-20T10:35:26.2666667+00:00

@Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) same problem.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,841 Reputation points Microsoft Vendor

2023-03-21T07:48:23.72+00:00

For this issue, it is recommended to open a support ticket for this. Please contact our paid phone support at MS Support. You will get 1:1 support on that.
Mario Mora 16 Reputation points

2023-09-15T10:47:44.29+00:00

Hi, I'm struggling with the same problem, static c++ libraries does not work for maui but it did on xamarin. It's a nuget project wrapping a bunch of c++ libs into a "iOS library" .net project type. I want to consume this nuget on a maui app

the problem is the native libraries are not being copied into the nuget package although you can see them added to the project, but actually are all missing

the native reference is added to the project the same exact way it's described above by Wael, but if you click on it on VS, there's no properties shown, if you do the same in the old xamarin ios project, you can see the props. don't know if that is related

Did anybody found a workaround for this?
Junior Jiang 6 Reputation points

2024-02-19T08:44:22.48+00:00

I aslo occurs this problem.

1 answer

Stefan Gstrein 0

This is my working solution:

I have my library in the root of my iOS Platforms directory: /Platforms/iOS/libCLib.iOS.a Important in the iOS Build settings: Linker behaviour for Debug has to be "Don't link" or "Link Framework SDKs Only".

<PropertyGroup Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">
    <MtouchLink>Full</MtouchLink>
    <AdditionalArgs>-cxx -gcc_flags "-L${ProjectDir} -lCLib.iOS -force_load ${ProjectDir}/libCLib.iOS.a"</AdditionalArgs>
</PropertyGroup>

<ItemGroup>
    <NativeReference Include="Platforms\iOS\libCLib.iOS.a" Kind="Static">
        <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </NativeReference>      
</ItemGroup>