(intro needed)

Any code for generating notifications that doesn't use WinRT API's should be written in the Microsoft.Toolkit.Uwp.Notifications.Shared project.

UWP-specific code can be written in the WinRT project library.

There's five notification projects...

• Shared
• NETStandard
• Portable
• WinRT
• UWP

The Shared project is where all the code is contained.

The other four projects are simply there so that the correct DLL's (and WINMD) can be built for specific platforms.

We use a Portable library that targets .NET 4.0, since the .NET Standard doesn't support 4.0 (it starts at 4.5). Therefore, projects that target .NET 4.0 can still use our library to generate notifications.

We then have the NET Standard library. This library can be used by any project targeting .NET 4.5, and is future-proof thanks to .NET Standard.

Finally there's the WinRT library and UWP libraries, which include some WinRT API's that only exist in WinRT. The UWP library is only for C#, while the WinRT library is a Windows Runtime Component for JavaScript and C++.

Imagine you add this library to a classic portable class library, and you also add it to your UWP app. In this case, your portable class library will receive the NETStandard dll (or the Portable dll if your library only targets 4.0). Your UWP project will receive the UWP dll.

Since these are two separate projects, you actually wouldn't be able to pass a ToastContent object from your portable class library to your UWP - that object is coming from a different DLL.

We fix this by making the names of the outputted DLL's the same. If two DLL's have the same name, only the one from the parent project (the UWP project in this case) is loaded. That means your portable class library will actually be using the UWP dll version at runtime, and you will be able to pass the ToastContent object from your portable class library to your UWP process.