fix(hotfix): skip CrestronOnvif.dll during assembly scanning at startup

[Copilot]

CrestronOnvif.dll is a Crestron-provided assembly that produces a spurious Invalid Image error on every Essentials startup when the program directory is scanned for device factories.

Changes

• DeviceFactory.cs: Introduced a assembliesToSkip list checked before each Assembly.LoadFrom() call; CrestronOnvif.dll is the first entry. Skipped assemblies emit a Verbose-level log instead of an error.

// Assemblies known to cause load errors that should be skipped
var assembliesToSkip = new[] { "CrestronOnvif.dll" };

foreach (var assembly in programAssemblies)
{
    if (assembliesToSkip.Any(a => Path.GetFileName(assembly).Equals(a, StringComparison.OrdinalIgnoreCase)))
    {
        Debug.LogMessage(LogEventLevel.Verbose, "Skipping assembly: {assemblyName}", null, assembly);
        continue;
    }
    // ...
}

The skip list is easily extensible if additional problematic Crestron assemblies are identified in the future.

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:

• crl.entrust.net
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Essentials/Essentials/PepperDash.Essentials.4Series.sln --packages /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/8E3C38744AF97AEA71D98A0334D7EC97/missingpackages_workingdir --packages /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/missingpackages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal --configfile /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/nugetconfig/nuget.config --force (dns block)
• ocsp.entrust.net
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /home/REDACTED/work/Essentials/Essentials/PepperDash.Essentials.4Series.sln --packages /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/8E3C38744AF97AEA71D98A0334D7EC97/missingpackages_workingdir --packages /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/missingpackages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal --configfile /tmp/codeql-scratch-34409fe8f58e31ec/dbs/csharp/working/nugetconfig/nuget.config --force (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)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[BUG]-CrestronOnvif.dll Invalid Image</issue_title>
<issue_description>Was this bug identified in a specific build version?
2.21.0

Describe the bug
A clear and concise description of what the bug is.
CrestronOnvif.dll is reporting an Invalid Image when Essentials starts. This has been happening for a while, but is more an annoyance and has not seemed to impact system performance.
Error reports regardless of config loaded.

Stacktrace

[2025-12-04 10:23:11.984][EROR][App 1] Unable to load assembly: /simpl/app01/CrestronOnvif.dll - Invalid Image

Essentials Version: 2.21.0
PepperDash Core Version: 2.21.0
Essentials Plugin Versions:
epi-vytio-iptv.4series Version: 0.6.0
KpmgRoom Version: 1.10.2
epi-videoCodec-ciscoExtended.4Series Version: 2.4.0
PepperDash.Essentials.DM Version: 1.5.4
epi-nanolumens-hseries.4Series Version: 1.1.0
epi-crestron-io.4Series Version: 2.1.1
epi-cisco-cli.4Series Version: 1.4.2
epi-display-samsung-mdc.4Series Version: 1.5.2
epi.analogWay.aquilon.4series Version: 1.3.1-cleanup-logging.1
Tesira-DSP-EPI.4Series Version: 3.3.0
epi-lutron-leap.4Series Version: 1.0.2
NvxEpi.4Series Version: 3.10.2

To Reproduce
Steps to reproduce the behavior:

1. Install Essentials
2. Monitor console at Error Level
3. See Error reported

Expected behavior
No error is expected.

Screenshots
NA

Additional context
NA
</issue_description>

<agent_instructions>when scanning assemblies at startup, we should skip attempting to load this particular assembly, tag the fix with a semantic hotfix</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@andrew-welker All the DLLs in the program folder are scanned when Essentials starts up to find devices/factories. This one is a Crestron-provided DLL that is loaded from the Crestron nuget packages. We can probably add something that filters this specific assembly out so the error message doesn't show up anymore.

• Fixes [BUG]-CrestronOnvif.dll Invalid Image #1365

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

Pull request overview

This hotfix prevents Essentials startup logs from being spammed by a known-bad Crestron-provided assembly (CrestronOnvif.dll) during the program-directory assembly scan used for device factory discovery.

Changes:

• Adds a small skip list to bypass loading CrestronOnvif.dll during startup DLL scanning.
• Logs skipped assemblies at Verbose level rather than emitting an error due to load failure.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[ngenovese11]

@andrew-welker @ndorin this fix has been verified functional in the field, have a look at your leisure