Could not load file or assembly 'Microsoft.Build The system cannot find the file specified. #517
Description
After a long debugging process, I've isolated the issue to a FileNotFoundException that occurs inside the dependabot-updater-nuget container. It seems the container image is missing the Microsoft.Build assembly required to parse .csproj files.
Environment:
OS:* Windows
CLI Tool:* dependabot-cli (Go version, installed via go install)
Container Runtime:* Podman
Ecosystem:* NuGet
Steps to Reproduce:
- Create a basic .NET 8 console application.
- Add an outdated dependency (e.g., dotnet add package Newtonsoft.Json --version 12.0.3).
- Create a dependabot.yml file in the project root:
version: 2
updates:
- package-ecosystem: "nuget"
directory: "/"
schedule:
interval: "daily"Command Executed:
dependabot update nuget --provider local .
Expected Behavior:
The tool should detect the outdated Newtonsoft.Json package and log a message that an update is available.
Actual Behavior:
The process fails. The logs show that after successfully starting the container, the updater throws a
System.IO.FileNotFoundException because it cannot find the Microsoft.Build assembly.
Full Log Output:
dependabot update nuget --provider local .
cli | 2025/09/24 15:31:25 Using hostname: github.com api endpoint: https://api.github.com
cli | 2025/09/24 15:31:25 Inserting $LOCAL_GITHUB_ACCESS_TOKEN into credentials
cli | 2025/09/24 15:31:27 image ghcr.io/github/dependabot-update-job-proxy/dependabot-update-job-proxy:latest is already up to date
cli | 2025/09/24 15:31:27 using image ghcr.io/github/dependabot-update-job-proxy/dependabot-update-job-proxy:latest at sha256:134b804c910426d5d5173c8e7f567bc1776f62c922bd39ae3db0b4d09e8821b7
cli | 2025/09/24 15:31:30 image ghcr.io/dependabot/dependabot-updater-nuget is already up to date
cli | 2025/09/24 15:31:30 using image ghcr.io/dependabot/dependabot-updater-nuget at sha256:1bc13ff32da65b9505044a29304b376e0adbb7266f575ad6cb0fa093f2f31f41
proxy | 2025/09/24 15:31:32 proxy starting, commit: 32f72c93e3b014db177b94dcad54e96d6e241a4a
proxy | 2025/09/24 15:31:32 Listening (:1080)
updater | Updating certificates in /etc/ssl/certs...
updater | rehash: warning: skipping ca-certificates.crt,it does not contain exactly one certificate or CRL
updater | 1 added, 0 removed; done.
updater | Running hooks in /etc/ca-certificates/update.d...
updater | done.
updater | Job: {
updater | "command": "update",
updater | "package-manager": "nuget",
updater | "allowed-updates": [
updater | {
updater | "update-type": "all"
updater | }
updater | ],
updater | "debug": false,
updater | "dependency-groups": [],
updater | "dependencies": null,
updater | "dependency-group-to-refresh": null,
updater | "existing-pull-requests": [],
updater | "existing-group-pull-requests": [],
updater | "experiments": null,
updater | "ignore-conditions": [],
updater | "lockfile-only": false,
updater | "requirements-update-strategy": null,
updater | "security-advisories": [],
updater | "security-updates-only": false,
updater | "source": {
updater | "provider": "local",
updater | "repo": ".",
updater | "directory": "/",
updater | "hostname": "github.com",
updater | "api-endpoint": "https://api.github.com"
updater | },
updater | "update-subdependencies": false,
updater | "updating-a-pull-request": false,
updater | "vendor-dependencies": false,
updater | "reject-external-code": false,
updater | "repo-private": false,
updater | "commit-message-options": null,
updater | "credentials-metadata": [
updater | {
updater | "host": "github.com",
updater | "type": "git_source"
updater | }
updater | ],
updater | "max-updater-run-time": 0,
updater | "exclude-paths": null,
updater | "multi-ecosystem-update": false
updater | }
updater | Unhandled exception: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Build, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
updater |
updater | File name: 'Microsoft.Build, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
updater | at NuGetUpdater.Core.Run.ApiModel.JobErrorBase.ErrorFromException(Exception ex, String jobId, String currentDirectory)
updater | at NuGetUpdater.Core.Clone.CloneWorker.RunAsync(Job job, String repoContentsPath) in /opt/nuget/lib/NuGetUpdater/NuGetUpdater.Core/Clone/CloneWorker.cs:line 80
updater | at NuGetUpdater.Core.Clone.CloneWorker.RunAsync(FileInfo jobFilePath, DirectoryInfo repoContentsPath) in /opt/nuget/lib/NuGetUpdater/NuGetUpdater.Core/Clone/CloneWorker.cs:line 56
updater | at NuGetUpdater.Cli.Commands.CloneCommand.<>c__DisplayClass4_0.<<GetCommand>b__0>d.MoveNext() in /opt/nuget/lib/NuGetUpdater/NuGetUpdater.Cli/Commands/CloneCommand.cs:line 43
updater | --- End of stack trace from previous location ---
updater | at System.CommandLine.Invocation.InvocationPipeline.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)
proxy | 2025/09/24 15:31:46 Skipping sending metrics because api endpoint is empty
proxy | 2025/09/24 15:31:46 0/0 calls cached (0%)
cli | 2025/09/24 15:31:48 updater failure: updater exited with code 1