Cannot load WebView2Loader.dll in Excel VSTO Add-In

[FROGGS]

Description I'm building a VSTO Add-In using Visual Studio 2019 on Windows 10. After adding the ribbon, windows form and the WebView2 user control I get an error message saying that said DLL cannot be found.

Version SDK: 1.0.1189-prerelease Runtime: Evergreen 99.0.1150.55 Framework: WinForms OS: Win10 21H2 Build 19044.1586

Repro Steps

• open Visual Studio 2019
• create new project
• search for VSTO
• select Excel-VSTP-Add-In
• name it excel-vsto-webview
• add a Ribbon (XML) via insert new element
• add custom ribbon code (XML) to show button near File->Save As
• initialize ribbon in addin class
• OK: pressing F5, creating empty workbook, clicking File, Save, My custom task, My Button results in a message box popup
• add a Windows Form via insert menu
• show form instead of message box in ribbon code (button click)
• OK: pressing F5, creating empty workbook, clicking File, Save, My custom task, My Button results in an empty Form window popping up
• add WebView2 NuGet package via package manager, version 1.0.1189-prerelease
• drag WebView2 Windows Forms control into Form1 using the designer
• OK: pressing F5, creating empty workbook, clicking File, Save, My custom task, My Button results in an empty Form window popping up
• adding webview2 init code from @cgeier https://github.com/MicrosoftEdge/WebView2Feedback/issues/187
• NOK: pressing F5, creating empty workbook, clicking File, Save, My custom task, My Button results in an empty Form window popping up plus error message, telling me it cant find a dll called WebView2Loader.dll

Screenshots

Additional context Repository containing exactly what is mentioned in repro steps: https://github.com/FROGGS/excel-vsto-webview

[FROGGS]

A workaround is to copy the WebView2Loader.dll to the Office16 program folder, but is there a better way?

[LK-Global]

We ran into a similar issue with an Office Add-in. We used procmon to see the progression of locations where the WebView2 dotNet assemblies is trying to load this WebView2Loader.dll. Eventually we moved the location where Office loads the WebView2 dotNet assemblies and made sure WebView2Loader.dll was located there as well.

[champnic]

I can't speak to cgeier's initialization code. As mentioned by @LK-Global some files may need to be included with your app if they aren't automatically being deployed. The list and expected locations are described here: https://docs.microsoft.com/en-us/microsoft-edge/webview2/concepts/distribution#files-to-ship-with-the-app

[cgeier]

@FROGGS: If using the initialization code that I posted in 187 double-check that the order of execution is as expected in your application. As of Webview2 version 1.0.664-prerelease/1.0.674.37, one can use CoreWebView2CreationProperties to specify properties such as UserDataFolder. For WPF, see 552 for how this can be used.