Why isn't my c++ dll properly loading into my c# exe?

Question

I'm continually getting this error message but I can't find the source. Here's a link to the .dll class I want to utilize:

link

And here's the c# class I'm calling it from:

link

Answer 1

There are two initial problems with the projects in the posted links.

1. The debug configuration of the C++ DLL project is configured to build an Application instead of a Dynamic Link Library.
2. After correcting to build a DLL the .Net application will not find it because the default location used for output from the C++ project is not searched. You can insert the fully qualified path to the DLL in the .Net code or have a post-build event to copy the C++ DLL to the .net bin sub-folders where the WPF application is located or change the C++ project property so that the DLL is created in the same folder that the WPF project uses for outputting its .exe

Answer 2

I quickly tested your DLL and you create m_pDirect2dFactory after InitD3D where you call it in

hr = m_pDirect2dFactory->CreateDxgiSurfaceRenderTarget(pBackBuffer, &props, &m_pBackBufferRT);

so it crashes as m_pDirect2dFactory = NULL.

(and you don't need any DLL for Direct2D, you can use P/Invoke in WPF (like in the WinUI 3 samples I posted...)