How to reference C# UWP Class Library from C++ UWP App


I am getting a COMException when trying to reference a method in a C# UWP class library from a C++ UWP app. This is happening with the most basic of setups, so I must be doing something wrong.


  1. Using Visual Studio (I'm using 16.5.4), Create a new "Blank App (Universal Windows - c++/CX)"
  2. Add to the solution a new "Windows Runtime Component (Universal Windows)", C#, Called "ClassLib"
  3. Add this method to Class1.cs: public static int GetNumber() { return 22; }
  4. Modify the MainPage constructor to look like this:
using namespace ClassLib;

    auto foo = Class1::GetNumber();
  1. Execute the application. This exception happens in the MainPage constructor:
Exception thrown at 0x76984402 in UWPApp.exe: 
  Microsoft C++ exception: 
    Platform::COMException ^ at memory location 0x0421DD44. 
    HRESULT:0x80131040 The text associated with this error code could not be found.
asked on Stack Overflow May 20, 2020 by Eric Jorgensen

1 Answer


This issue is due to calling .net based WinRT components from C++/CX or C++ WinRT projects. To make it work, you can add Microsoft.Net.Native.Compiler nuget package in your c++/cx project and install it first. Then Right-click the project -> Unload Project -> Edit .vcxproj. After that, adding the following properties in it.

    <UseDotNetNativeToolchain Condition="'$(Configuration)'=='Release'">true</UseDotNetNativeToolchain>

Note that, replace the 2.2.3 version above with the version of Microsoft.Net.Native.Compiler nuget package you installed. For more details about it, you can refer to this similar thread.

answered on Stack Overflow May 21, 2020 by Faywang - MSFT

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