Unable to load DLL 'libuv' after migrating to Visual Studio 2017

My project was created in VS 2015, targeting net461.

I migrated to VS 2017, now I can't run my application when Targeting Platform is set to x64 or AnyCPU.

works when Targeting Platform is set to x86.

when Targeting Platform is set to x64 or AnyCPU I get this error at this line:
host.Run();

Error

Unhandled Exception: System.AggregateException: One or more errors occurred. ---> System.DllNotFoundException: Unable to load DLL 'libuv': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.Libuv.NativeMethods.uv_loop_size()
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvLoopHandle.Init(Libuv uv)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.KestrelThread.ThreadStart(Object parameter)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.KestrelEngine.Start(Int32 count)
   at Microsoft.AspNetCore.Server.Kestrel.KestrelServer.Start[TContext](IHttpApplication`1 application)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.Start()
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(IWebHost host, CancellationToken token, String shutdownMessage)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(IWebHost host)
   at Api.Program.Main(String[] args)
)

Error is occurring in both IIS Express and IIS.

I want to be able to build and run in IIS either targeting x64 or AnyCPU.

[natemcmaster]

@capiono can you share your *.csproj file?

[BorisDli]

In host.Run();
Error
System.AggregateException: 'One or more errors occurred.'
BadImageFormatException: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)

[natemcmaster]

@BorisDli can you share your *.csproj file? We suspect this is an error in .NET Core SDK, not Kestrel itself, but it's hard to know without a repro.

[BorisDli]

MVCtaghelperscheckboxes.csproj.txt

[natemcmaster]

Thanks, that helps. Your csproj has these lines:

  <PropertyGroup>
    <TargetFramework>net461</TargetFramework>
    <RuntimeIdentifier>win7-x86</RuntimeIdentifier>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
    <PlatformTarget>AnyCPU</PlatformTarget>
  </PropertyGroup>

There is a conflict in your project about which CPU architecture to target. The line <RuntimeIdentifier>win7-x86</RuntimeIdentifier> instructs NuGet to use the x86 version of LibUV (a native I/O library used by Kestrel's) and <PlatformTarget>AnyCPU</PlatformTarget> instructs the app to compile as AnyCPU, which means the process may run as x64. This mismatch is likely the source of the error. As @nguerrera points out dotnet/sdk#1017 (comment), this isn't something the SDK currently warns you about --- though hopefully it will in future versions.

I'd recommend removing RuntimeIdentifier unless there is some other reason you need it.

[natemcmaster]

Closing as external to Kestrel. @capiono if you've identified an error not solved by my previous comments, we can re-open for further investigation.