Type identity CoreWebView2 types is different between WinUI 3 and WPF/WinForms

[Eilon]

Description

I'm trying to share code across all my usage of WebView2 as much as possible. Of course the controls for WinUI, WPF, and WinForms are all different, because each UI framework is different. But even seemingly platform-independent types, such as CoreWebView2 have different identities. This makes it impossible to build a class library targetting CoreWebView2 and run on all platforms.

CoreWebView2 in WinUI 3 has this identity:

• Type name: Microsoft.Web.WebView2.Core.CoreWebView2 (same)
• Assembly: Microsoft.WinUI, Version=3.0.0.0, Culture=neutral, PublicKeyToken=de31ebe4ad15742b (different)

CoreWebView2 in WPF/WinForms has this identity:

• Type name: Microsoft.Web.WebView2.Core.CoreWebView2 (same)
• Assembly: Microsoft.Web.WebView2.Core, Version=1.0.705.50, Culture=neutral, PublicKeyToken=2a8ab48044d2601e (different)
• NuGet package version: 1.0.705.50

Version
SDK: NuGet 1.0.705.50
Runtime: N/A
Framework: WPF/WinForms and WinUI
OS: N/A

Repro Steps

1. Build a class library that uses CoreWebView2 from the WebView2 NuGet package for WPF/Winforms.
2. Try to have that class library also support the WinUI CoreWebView2

Result: You can't, because the type identities are different.
Expected: The type identities of platform-independent types should be identical.

Additional context

We encountered this while working on Blazor Desktop, where we support hosting Blazor directly in WPF and WinForms, and also in WinUI (via .NET MAUI). We wanted to put most of our code in a common WebView2-aware library, and then only write thin adapters to wire it up to each UI platform. However, this is not possible because the type identities are different, so we have to duplicate all the code.

AB#33281317

[david-risney]

WebView2 supports Win7+ for its .NET and COM API (and WinForms/WPF controls) and Win10 for the WinRT API used by WinUI3. On Win7 we can't use WinRT since that was introduced in Win8 but WinUI3 is based on WinRT and we must use WinRT for WinUI3. This is why the types are different between the WinUI3 WebView2 control and the WinForms/WPF WebView2 controls. Unfortunately I'm not sure what we could do differently.

[Eilon]

There are probably some .NET tricks that can be done to maintain the same identity. The code doesn't need to be the same at all. You just need 2 DLLs with the same name/publickeytoken/etc. They can each reference their own dependencies. The WinUI DLL just needs the CoreWebView2 types moved to a separate assembly (perhaps in the same NuGet package), and that separate assembly needs to be built with the same identity as what's used in WPF/WinForms. Or, don't even move any code, but add the 2nd assembly (named the same as WinForms/WPF) and include Type Forwarders to redirect the types to the WinUI assembly.

There could be reasons why this wouldn't work, but I think it ought to.

[david-risney]

I'm not sure its possible to ensure the types match. WinRT types can only refer to other WinRT types. The projection of WinRT into .NET does mapping between some WinRT types and .NET types but not all of them. For example, IIRC WinRT async methods in .NET still rely on Windows.Foundation.Async* types and WinRT events in .NET use Windows.Foundation.TypedEventHandler - types that won't exist on Win7. I wonder if c#/winrt helps with any of this. I'll try to find someone who owns winrt projection and can tell me more.

[Eilon]

Hmm I didn't realize the APIs for CoreWebView2 are so different I just diffed them and there are a few categories of differences:

1. Async stuff uses a different pattern: Task<T> vs. IAsyncOperation<T> / IAsyncAction.
2. Event handlers use a different pattern: EventHandler<T> vs. TypedEventHandler<TSender, T>.
3. Major API deltas, such as WinUI having some additional APIs for "vritual host name to folder mapping"
4. Minor API deltas, such as WinUI implementing FromAbi, Equals, operators for == and !=, and overriding Equals/GetHashCode

Would it be possible in WinUI to have all of this stuff purely internal, and also include a managed wrapper that makes all the APIs have the same identity as WPF/WinForms?

I think it would be really nice to be able to write code once and use it in all WebView2's, but maybe that's a problem unique to what we're doing with Blazor Desktop because we're trying to target every WebView2 on every platform.

We can continue building our own WebView2 abstractions but that solves the problem only for us and not for any other consumers.

[champnic]

I've added this as a scenario on our backlog (link AB#33281317).