UWP C# app calling Windows Runtime Component written in C++ - c++

Question

I am trying to create a Windows Runtime(WinRT) Component written in C++(c++-cx) which can be called from my UWP C# app. I followed this MSDN Tutorial
It all went fine. I am able to build & run the code/sample specified in the above link on both Windows-10 Desktop & Mobile
I then tried to create a even simpler WinRT Component. I followed the same steps as above tutorial. Created a Windows Runtime Component project (File->New->Project->Visual C++ ->Windows->Universal->Windows Runtime Component(Universal Windows))
Now my class has only one function, getNum which basically returns a uint16
This is my Class header file
#pragma once
#include <collection.h>
namespace WRT_sample
{
public ref class Class1 sealed
{
public:
Class1();
uint16 getNum();
};
}
This is the corresponding cpp file:
#include "Class1.h"
using namespace WRT_sample;
using namespace Platform;
Class1::Class1()
{
}
uint16 Class1::getNum()
{
return 100;
}
I am using the same class names(Class1.h & Class1.cpp) which VS-2015 provides when I create a new WinRT project.
This is how I make a call to WinRT class from my C# code:
namespace CS_WRT_sample
{
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
initWRT();
}
void initWRT()
{
try
{
var nativeObj = new Class1();
var num = nativeObj.getNum();
this.Result2.Text = "Num from Cpp: " + num.ToString();
Debug.WriteLine("Num from Cpp: " + num);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
this.Result3.Text = ex.Message;
}
}
}
}
I am able to build & run my code on Desktop(x86/x64 Local Machine), but when I try to run on Mobile(x86 Emulator or ARM device), it fails with the following error:
Exception thrown: 'System.IO.FileNotFoundException' in CS_WRT_sample.exe
The specified module could not be found. (Exception from HRESULT: 0x8007007E)**
This is the stack trace which I see:
System.StubHelpers.StubHelpers.GetWinRTFactoryObject(IntPtr pCPCMD)
at WRT_sample.Class1..ctor()
at CS_WRT_sample.MainPage.initWRT()
My VS-2015 details:
MS Visual Studio Professional 2015
Version 14.0.25123.00 Update 2
MS .NET Framework
Version 4.6.01038
I am not sure, why I am hitting the issue, as I followed the same steps mentioned in the MSDN tutorial.
Any help will be highly appreciated.

Answer 1

You will run into this if you use a direct reference to a C++ winmd, instead of a P2P reference. This is easy to check in your .csproj:
For example, your .csproj should not have this line:
..\Debug\Abc_def\Abc_Def.winmd
Instead, consider using something like:
{1ee77824-eaa8-40f1-9b56-6f8ffa44e727}
Abc_Def