Migrate to .slnx solution format exclusively

[Copilot]

Overview

This PR migrates the repository from the traditional .sln format to the modern .slnx solution file format exclusively, removing the legacy .sln file to avoid CI/CD conflicts.

Changes

• Generated EssentialCSharp.Web.slnx using dotnet sln migrate command
• Removed the traditional EssentialCSharp.Web.sln file to prevent "multiple solution files" errors in CI
• Updated Dockerfile to reference .slnx instead of .sln

Why This Change?

The .slnx format is the modern solution file format introduced in recent .NET SDK versions. It provides:

• Cleaner format: 19 lines vs 63 lines (846 bytes vs 3.8KB)
• Better readability: Human-friendly XML structure
• Forward compatibility: Prepares the repository for future .NET tooling that may prefer or require this format
• CI/CD compatibility: Having only one solution file prevents ambiguity errors when dotnet commands don't specify which solution to use

By using only the .slnx format, we eliminate the MSB1011 error that occurred when multiple solution files were present in the same directory.

Verification

The .slnx solution file has been verified to work correctly:

• ✅ dotnet restore automatically finds and uses the .slnx file
• ✅ dotnet build works without specifying a solution file
• ✅ dotnet test runs successfully (54/55 tests pass - one pre-existing network connectivity test failure)
• ✅ Dockerfile updated to explicitly reference .slnx for Docker builds

References

• Microsoft Documentation: dotnet sln migrate

Original prompt

run dotnet sln migrate (https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-sln#migrate) to add in a .slnx file to live alongside our .sln file for now (.sln for backwards compatibility for now)

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[BenjaminMichaelis]

@copilot maybe we can drop the .sln file and just keep the .slnx?

We get this otherwise.

Run dotnet restore
dotnet restore
shell: /usr/bin/pwsh -command ". '{0}'"
env:
DOTNET_ROOT: /usr/share/dotnet
MSBUILD : error MSB1011: Specify which project or solution file to use because this folder contains more than one project or solution file.
Error: Process completed with exit code 1.

[Copilot]

@copilot maybe we can drop the .sln file and just keep the .slnx?

We get this otherwise.
...

Done in commit 38e768f. The .sln file has been removed and the Dockerfile updated to reference EssentialCSharp.Web.slnx. This resolves the CI error about multiple solution files.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.hcaptcha.com
  • Triggering command: /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/EssentialCSharp.Web/EssentialCSharp.Web/EssentialCSharp.Web.Tests/bin/Release/net9.0/EssentialCSharp.Web.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/EssentialCSharp.Web/EssentialCSharp.Web/EssentialCSharp.Web.Tests/bin/Release/net9.0/EssentialCSharp.Web.Tests.deps.json /home/REDACTED/work/EssentialCSharp.Web/EssentialCSharp.Web/EssentialCSharp.Web.Tests/bin/Release/net9.0/testhost.dll --port 40703 --endpoint 127.0.0.1:040703 --role client --parentprocessid 4306 --telemetryoptedin false (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[Copilot]

Pull Request Overview

This PR migrates the repository from the traditional .sln format to the modern .slnx solution file format exclusively, removing the legacy file to prevent CI/CD conflicts and embrace the newer, more readable XML-based solution format.

• Generated new EssentialCSharp.Web.slnx file using dotnet sln migrate command
• Removed the traditional 63-line .sln file in favor of the 19-line .slnx format
• Updated Dockerfile references to use the new solution file format

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
EssentialCSharp.Web.slnx	New XML-based solution file containing all project references and solution items
EssentialCSharp.Web.sln	Removed traditional solution file to prevent multiple solution file conflicts
EssentialCSharp.Web/Dockerfile	Updated dotnet commands to reference .slnx instead of .sln file