[Problem/Bug]: v150.0.4078.83 regression - CoreWebView2.DownloadStarting not triggered when DefaultDownloadFolderPath contains trailing backslash

What happened?

After upgrading the runtime to version 150, the CoreWebView2 event DownloadStarting is not getting triggered anymore in case that DefaultDownloadFolderPath contains a valid path that is ending with a backslash.

In earlier versions, lower than 150, this issue did not occur.

Importance

Important. My app's user experience is significantly compromised.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

150.0.4078.65

SDK Version

No response

Framework

WPF

Operating System

Windows 11

OS Version

26200.8655

Repro steps

In a test application containing a WebView2

• register event handler for CoreWebView2.DownloadStarting
• In the event handler, set Handled and Cancel to True
• Set WebViewControl.CoreWebView2.Profile.DefaultDownloadFolderPath to a valid path with a trailing backslash
  for example: C:\Users\<user>\AppData\Local\Temp\
• Navigate to a file via CoreWebView2.Navigate(url)
  for example https://aka.ms/vs/17/release/vc_redist.x64.exe

Result: The DownloadStarting event is not triggered and the Save As dialog appears
Remove the trailing backslash from the DefaultDownloadFolderPath and repeat the test: The event is triggered and the download can be cancelled.

Attached you find a small test .net project that allows you to test it without and with trailing backslash to reproduce the issue.

WebView2DownloadRepro.zip

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

Regression in newer Runtime

Last working version (if regression)

< 150