[Problem/Bug]: Could not load file or assembly 'Microsoft.Web.WebView2.Core' on .Net 9 MAUI

[DharshanBJ]

What happened?

We are experiencing an issue with our packages (produced from this repo: https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/main/Directory.Packages.props#L16) that have a dependency on the WebView2 package. When an application using our packages upgrades to .NET 9 MAUI, it crashes with the following exception:

System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Web.WebView2.Core, Version=1.0.2739.15, Culture=neutral'. Could not load file or assembly 'Microsoft.Web.WebView2.Core, Version=1.0.864.35, Culture=neutral, PublicKeyToken=2a8ab48044d2601e'. The system cannot find the file specified.

This issue did not occur with .NET 8 MAUI, but started after upgrading to .NET 9 MAUI. This seems similar to the issue described in WebView2Feedback#4784.

Even after upgrading the WebView2 version to 1.0.2903.40(which should have the fix for #4784), we are still encountering the same issue.

Refere this issue for more details - AzureAD/microsoft-authentication-library-for-dotnet#4933

Importance

Blocking. My app's basic functions are not working due to this issue.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

1.0.2903.40

SDK Version

No response

Framework

WinUI3/WinAppSDK

Operating System

Windows 11

OS Version

No response

Repro steps

This is a simple VS Solution containing a .Net8 and a .Net9 version of the same project. The .Net8 works but the .Net9 does not. https://github.com/user-attachments/files/18798538/MauiMSAL-Test.zip

if you try the .Net9 version you get this error : 'Could not load file or assembly 'Microsoft.Web.WebView2.Core, Version=1.0.864.35, Culture=neutral, PublicKeyToken=2a8ab48044d2601e'. The system cannot find the file specified.'

The csproj files in https://github.com/user-attachments/files/18798538/MauiMSAL-Test.zip have the Maui/.Net/winappsdk versions that causes this issue.

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

No, this never worked

Last working version (if regression)

No response

[Navdeep-ss]

@DharshanBJ
The solution file you shared, I am able to build this for both .net8 and .net9 in visual studio 2022

with the webview2 SDK version 1.0.2792.45

[unrateddi]

Hi @Navdeep-ss , the issue occurs at runtime. Please run the MauiMSAL-9 project and hit the Login button.

[Navdeep-ss]

The Microsoft.Maui.Controls package version 9.0.30 requires Microsoft.Web.WebView2 version 1.0.2792.45 or higher. However, your project is currently using Microsoft.Web.WebView2 version 1.0.864.35. This discrepancy is causing your code to expect a binary for WebView2 version 1.0.864.35, while the available binary version is 1.0.2792.45.

Here is the dependency flow:

graph TD;
    A[Microsoft.Maui.Controls 9.0.30] --> B[Microsoft.Maui.Controls.Core 9.0.30];
    B --> C[Microsoft.Maui.Core 9.0.30];
    C --> D["Microsoft.Web.WebView2 (>= 1.0.2792.45)"];

Loading

You can see the dependency section here

The .NET 9 version has a dependency on WebView2 version 1.0.2792.45 or higher, whereas the .NET 8 version did not have this dependency. You can verify this here

Unfortunately, there is nothing we can do on our end to support your scenario. You will need to update the WebView2 version if you want to use it with MAUI .NET 9.

[mibinoob]

@Navdeep-ss You are plain wrong.
While your statement about package version and requirements are completely correct the issue @unrateddi points out is the core of the problem. I can promise you he has no reference whatsoever to webview version 1.0.864.35 and runs the newest version of webview.

However during runtime, as @unrateddi states, the compiler explicitly asks for webview version 1.0.864.35, and only by downgrading to this version, the webview window to enter login options can be shown.

This, as your dependency flow shows, cannot work on NET9 (among other things), and is the story that brought us here.

Upgrading is simply not an option

EDIT: It is true NET 8 did not have this dependency, however, on NET 8 running newest webview version and sdk 1.6 with MSAL 4.66 likewise gives the same issue, where it compiles but webview window cannot load because webview 1.0.864.35 is required for it to run

[Navdeep-ss]

I see this dependency explicity stated in your Directory.Packages.props.
Are you saying this line is autogenerated?

[mibinoob]

Maybe. Maybe not.
I am asking you to review the image, which shows the core of the issue. Running any other version of webview than 1.0.864.35 simply doesn't work. I highly suggest you read all of AzureAD/microsoft-authentication-library-for-dotnet#4933 for more knowledge

[Navdeep-ss]

@DharshanBJ does even after these AzureAD/microsoft-authentication-library-for-dotnet#5154 changes, you are getting the same error.
In my knowledge the changes in the pr should have fixed the issue?

[Navdeep-ss]

@Navdeep-ss You are plain wrong. While your statement about package version and requirements are completely correct the issue @unrateddi points out is the core of the problem. I can promise you he has no reference whatsoever to webview version 1.0.864.35 and runs the newest version of webview.

However during runtime, as @unrateddi states, the compiler explicitly asks for webview version 1.0.864.35, and only by downgrading to this version, the webview window to enter login options can be shown.

This, as your dependency flow shows, cannot work on NET9 (among other things), and is the story that brought us here.

Upgrading is simply not an option

EDIT: It is true NET 8 did not have this dependency, however, on NET 8 running newest webview version and sdk 1.6 with MSAL 4.66 likewise gives the same issue, where it compiles but webview window cannot load because webview 1.0.864.35 is required for it to run

Just a FYI. The repro solution fails for dot net 8 too with the same error

if you add this line to the csproj file

which specifies that the project should use version 1.0.2739.15. As I mentioned earlier, the issue arises because the library expects version 1.0.864.35, but it is not receiving that version.

For .NET 8, things used to work because there was no directive telling the build to use any version other than 1.0.864.35. However, if we explicitly state in the .csproj to use a different version, it fails.

In the case of .NET 9, MAUI has a dependency on a WebView2 version greater than 1.0.864.35. So, even if you do not explicitly state in your project to NOT use version 1.0.864.35, due to dependency resolution, your solution builds with version 1.0.2792.45. However, at runtime, the library you are using expects version 1.0.864.35, which leads to a runtime file not found error.

[DharshanBJ]

@DharshanBJ does even after these AzureAD/microsoft-authentication-library-for-dotnet#5154 changes, you are getting the same error. In my knowledge the changes in the pr should have fixed the issue?

Hi @Navdeep-ss, we are getting the same error even after upgrading the webview2 version to 1.0.2903.40 here - https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/d0a3fc04980174a61c2ec6434dd28dc626674b92/Directory.Packages.props#L16.

Infact, after making this change, we see this issue on both .Net 8 and .Net 9 MAUI.

[Navdeep-ss]

@DharshanBJ, I’ve identified the reason why we’re still encountering this error even after the version update.

and for now it could be fixed just by adding

 <WebView2EnableCsWinRTProjection>false</WebView2EnableCsWinRTProjection>

in your csproj of the projects which refer your package.

To understand why this is happening we have to go through the nuget package of webview2 mainly these lines of Common.targets

If you see if WebView2EnableCsWinRTProjection is true it will copy Microsoft.Web.Webview2.Core.dll from $(NugetRoot)\runtimes\win-$(EffectivePlatform)\native_uap path to you out bin folder, which is winrt specific dll

But in the repro sample app, this WebView2EnableCsWinRTProjection turns out to be true by default, so it will only execute the first When inside Choose.

Given Microsoft.Identity.Client.Desktop project is targeted for net462 and netcoreapp3.1, it would have required dll from $(NugetRoot)\lib_manual\netcoreapp3.0\Microsoft.Web.WebView2.Core.dll but its getting different dll copied to the project's out bin folder which ends up creating file not found exception at runtime.

The best way to avoid that error for now is just use

<WebView2EnableCsWinRTProjection>false</WebView2EnableCsWinRTProjection>

in the csproj of the app you are using this library with.

This issue occurs because Common.targets was written with the assumption that WebView would be the primary dependency. Some of the logic does not function correctly when WebView is only a transient dependency.

[DharshanBJ]

@Navdeep-ss
Thank you for looking into this. We have a large number of customers facing this issue, and I'm concerned that they might not be aware that they need to add this additional line of code in their projects to work around the problem. Is this information documented anywhere?

Additionally, will there be a proper fix for this issue in the future?