[ARM64] BadImageFormatException when running on Windows 11 ARM64 with .NET Framework 4.8

[Taiizor]

Environment

• Device: Microsoft Surface Pro 10
• OS: Windows 11 ARM64 (10.0.22631.5624)
• Architecture: ARM64
• Framework: .NET Framework 4.8
• CefSharp Version: 139.0.280.0 (ARM64 build)
• VC++ Redist: v14.44.35208.00

Issue

When running my application on Windows 11 ARM64, I get the following error:

System.BadImageFormatException: 
Could not load file or assembly 'CefSharp.Core.Runtime, Version=139.0.280.0, Culture=neutral, PublicKeyToken=40c4b6fc221f4138' or one of its dependencies. An attempt was made to load a program with an incorrect format.

{
    "HResult": -2147024885,
    "Source": "CefSharp.Core",
    "HelpURL": null,
    "Message": "Could not load file or assembly 'CefSharp.Core.Runtime, Version=139.0.280.0, Culture=neutral, PublicKeyToken=40c4b6fc221f4138' or one of its dependencies. An attempt was made to load a program with an incorrect format.",
    "ClassName": "System.BadImageFormatException",
    "Data": {
      "System.Object": null
    },
    "FullMessage": "Could not load file or assembly 'CefSharp.Core.Runtime, Version=139.0.280.0, Culture=neutral, PublicKeyToken=40c4b6fc221f4138' or one of its dependencies. An attempt was made to load a program with an incorrect format.",
    "RawStackTrace": "   at CefSharp.CefSettingsBase..ctor()\r\n   at CefSharp.Wpf.HwndHost.CefSettings..ctor()\r\n   at Sucrose.Live.CefSharp.App.Configure() in E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs:line 305\r\n   at Sucrose.Live.CefSharp.App.Checker() in E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs:line 219\r\n   at Sucrose.Live.CefSharp.App.OnStartup(StartupEventArgs e) in E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs:line 623\r\n   at System.Windows.Application.<.ctor>b__1_0(Object unused)\r\n   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)\r\n   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)",
    "StackTrace": [
      {
        "Method": "Void .ctor()",
        "LineNumber": 0,
        "FileName": null,
        "ColumnNumber": 0
      },
      {
        "Method": "Void .ctor()",
        "LineNumber": 0,
        "FileName": null,
        "ColumnNumber": 0
      },
      {
        "Method": "Void Configure()",
        "LineNumber": 305,
        "FileName": "E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs",
        "ColumnNumber": 25
      },
      {
        "Method": "Void Checker()",
        "LineNumber": 219,
        "FileName": "E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs",
        "ColumnNumber": 17
      },
      {
        "Method": "Void OnStartup(System.Windows.StartupEventArgs)",
        "LineNumber": 623,
        "FileName": "E:\\MyProject\\Sucrose\\Pro\\Sucrose\\src\\Live\\Sucrose.Live.CefSharp\\App.xaml.cs",
        "ColumnNumber": 21
      },
      {
        "Method": "System.Object <.ctor>b__1_0(System.Object)",
        "LineNumber": 0,
        "FileName": null,
        "ColumnNumber": 0
      },
      {
        "Method": "System.Object InternalRealCall(System.Delegate, System.Object, Int32)",
        "LineNumber": 0,
        "FileName": null,
        "ColumnNumber": 0
      },
      {
        "Method": "System.Object TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)",
        "LineNumber": 0,
        "FileName": null,
        "ColumnNumber": 0
      }
    ],
    "InnerException": null
  }

Repro Steps

1. Build a .NET Framework 4.8 WPF application with ARM64 target.
2. Reference CefSharp.Wpf (ARM64) v139.0.280.0.
3. Run on Windows 11 ARM64 (Surface Pro 10).
4. Observe the BadImageFormatException.

Additional Information

• In my project, CefSharp is included as a module (separate project).
• Other architectures (x86/x64) work fine.
• Error indicates an architecture mismatch, but I am explicitly using the ARM64 build.
• VC++ Redist v14.44.35208.00 is installed.
• Related project repo (for context): https://github.com/Taiizor/Sucrose

Question

• Is the ARM64 support for CefSharp (>=94.4.20) intended to work with .NET Framework 4.8 applications?
• Are there any additional steps required to make the ARM64 build run correctly on Windows 11 ARM64?
• Could this be a packaging/runtime deployment issue (e.g., native dependencies not copied correctly), or is there a limitation in ARM64 support for .NET Framework?

Thanks for your great work on CefSharp 🙏

[amaitland]

Is the ARM64 support for CefSharp (>=94.4.20) intended to work with .NET Framework 4.8 applications?

Not yet. It's technically possible, just support hasn't been added. More details in #4155

• Are there any additional steps required to make the ARM64 build run correctly on Windows 11 ARM64?

Targeting .Net 6 or greater is currently the only option.

• Could this be a packaging/runtime deployment issue (e.g., native dependencies not copied correctly), or is there a limitation in ARM64 support for .NET Framework?

• Related project repo (for context): https://github.com/Taiizor/Sucrose

Interesting project, looks very cool 🥇

[Taiizor]

Is the ARM64 support for CefSharp (>=94.4.20) intended to work with .NET Framework 4.8 applications?

Not yet. It's technically possible, just support hasn't been added. More details in #4155

• Are there any additional steps required to make the ARM64 build run correctly on Windows 11 ARM64?

Targeting .Net 6 or greater is currently the only option.

• Could this be a packaging/runtime deployment issue (e.g., native dependencies not copied correctly), or is there a limitation in ARM64 support for .NET Framework?

• Related project repo (for context): https://github.com/Taiizor/Sucrose

Interesting project, looks very cool 🥇

It was very difficult, but I managed to make my project work with .NET 9, except for the Bundle [Setup]. Of course, the hard part was making different applications run with a shared framework from a common folder, even if .NET 9 was not installed on the device. I decided to keep the Bundle project on .NET Framework 4.8 so that it can run on almost every device.

[amaitland]

If you have time/motivation then a PR to add support for the .net framework packages would be most welcome.

I don't own an arm64 machine, so I cannot practically add support myself.

[Taiizor]

If you have time/motivation then a PR to add support for the .net framework packages would be most welcome.

I don't own an arm64 machine, so I cannot practically add support myself.

I don’t have an ARM64 device either, it’s just that when publishing an app to the Microsoft Store, the reviewers test my app on an ARM64 device, and that’s why I’m here right now (: