Using WebView2 with MSAL.NET

發行項
09/11/2023

WebView2 is a modern embedded browser runtime based on Microsoft Edge, capable of performing Windows Hello authentication, log in with FIDO keys, and more. This browser replaces the legacy web view based on Internet Explorer.

Availability

To use WebView2 in your application, the following requirements must be met:

Windows 10 OS or newer (supported by the WebView2 runtime).
MSAL.NET version 4.28.0 and higher.
WebView2 runtime must be installed on the machine.

Call pattern

When attempting to use the new WebView2 runtime, keep in mind the following required changes:

In applications written against net6.0-windows or newer, no changes are necessary.
In applications written against .NET Framework, .NET Core, or base .NET 5 or above, add a reference to Microsoft.Identity.Client.Desktop and add .WithWindowsEmbeddedBrowserSupport() when instantiating the public client application.

var pca = PublicClientApplicationBuilder
        .Create("0f887a65-3c78-4b16-9529-6209b8741c26")
        .WithWindowsEmbeddedBrowserSupport()
        .Build();

Important

WebView2 is not supported for Microsoft Entra ID (formerly known as Azure Active Directory) authorities. Using .WithWindowsEmbeddedBrowserSupport() in that context is always going to default to the legacy web view, regardless of the setting provided during the instantiation of the public client application. This is caused by stability bugs identified during MSAL development. For B2C and Active Directory Federation Services (ADFS) authorities, WebView2 will be shown.

Behaviour

Framework	Embedded web view	Default web view
.NET Framework	Legacy, WebView2 with fallback to Legacy¹	Legacy embedded
.NET Core	WebView2 with fallback to Legacy²	System
.NET 6³	WebView2 with fallback to Legacy²	System
.NET 6 Windows	WebView2, fallback to Legacy	WebView2, embedded

¹ Legacy web view is the default in .NET Framework apps. WebView2 can be used via Microsoft.Identiy.Client.Desktop package. ² .NET Core and .NET 6+ apps can only use web view via Microsoft.Identity.Client package. ³ MSAL.NET doesn't provide explicit net5.0 binaries. .NET 5 apps will follow .NET Core behavior.

Troubleshooting

WebView2 on .NET Framework

There's a scenario when an app that targets .NET Framework and references the MSAL.NET NuGet package tries to acquire token interactively with WebView2 embedded browser, WebView2 will throw exceptions. These errors can be System.BadImageFormatException: An attempt was made to load a program with an incorrect format. or System.DllNotFoundException: 'Unable to load DLL 'WebView2Loader.dll': The specified module could not be found. As of MSAL.NET 4.32.0 these exceptions are wrapped into MsalClientException.

This occurs due to an existing bug in the WebView2 SDK on the .NET Framework platform because the library cannot figure out the target platform of its dependencies. One workaround is to add a <PlatformTarget> with values AnyCPU, x86, or x64 to your application project file. x86 or x64 have to match the target framework of the WebView2 installed on the machine. Another workaround is to add <PlatformTarget>AnyCPU</PlatformTarget> in your app's project file and also directly reference the WebView2 NuGet package. For details, see issues #2482, #730.

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