WPF content files don't work with single-file

[ericstj]

Description

Create a WPF application that uses ContentFiles

When run outside single file this works and can load content.

When run under singlefile this fails because this throws:

wpf/src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/AppModel/ContentFilePart.cs

Line 113 in eaece0a

entryLocation = new Uri(Application.ResourceAssembly.CodeBase);

Resulting in null return value which later throws here:

wpf/src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/AppModel/ContentFilePart.cs

Line 76 in eaece0a

Uri file = new Uri(codeBase, filePath);

Most likely this ContentFilePart needs to "know" about single-file and be able to fetch it's content file.

System.ArgumentNullException: Value cannot be null. (Parameter 'baseUri')
   at System.Uri..ctor(Uri baseUri, String relativeUri)
   at MS.Internal.AppModel.ContentFilePart.GetStreamCore(FileMode mode, FileAccess access)
   at System.IO.Packaging.PackagePart.GetStream(FileMode mode, FileAccess access)
   at MS.Internal.IO.Packaging.PackagePartExtensions.GetSeekableStream(PackagePart packPart, FileMode mode, FileAccess access)
   at MS.Internal.IO.Packaging.PackagePartExtensions.GetSeekableStream(PackagePart packPart)
   at System.Windows.Application.GetContentStream(Uri uriContent)
   at wpf.MainWindow..ctor()

Configuration

net5.0-windows, 5.0.0-rc.2.20464.8, publishSingleFile, win-x64

Regression?

No, single file WPF didn't work until RC2

Other information

Repro:
wpf.zip

To repro run dotnet publish -p:PublishSingleFile=true -r:win-x64 -f:net5.0-windows

Compare execution of normal vs single file app.

[ghost]

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

[agocke]

The behavior in single-file publishing looks by-design to me: https://github.com/dotnet/designs/blob/main/accepted/2020/single-file/design.md

I think this issue is more appropriate for the WPF repo

[Sewer56]

Regression?

No, single file WPF didn't work until RC2

This is a regression (since Preview 8).

Although single file self-contained WPF applications didn't work until RC2, framework-dependent applications did.
Due to the same issue, framework-dependent applications no longer function at the current moment in time.

[Sewer56]

Bumping this issue after 2 years as I want to express my continued interest.
The regression is (in the context of framework dependent single file) is still here today and despite the milestone; this issue hasn't been assigned onto any of the repository projects.