# Validate Sdk > Install and validate a .NET SDK from an Azure DevOps internal build. Use this when asked to install, validate, or set up a .NET SDK from a dnceng/internal Azure DevOps build link or build ID. - Skill: `dotnet/validate-sdk` (Agent Skill) - Install (CLI): `npx skillmds@latest add dotnet/validate-sdk` - Raw SKILL.md: https://api.skillmd.com/api/skills/dotnet/validate-sdk/raw - Safety review: pending (external: skill-scanner WARNING, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: DevOps & Infra - Author: .NET (Microsoft) (https://skillmd.com/u/dotnet) - Updated: 2026-09-09 - Page: https://skillmd.com/skills/dotnet/validate-sdk --- # Install and Validate .NET SDK from Azure DevOps Internal Build Follow these steps to install and validate a .NET SDK from an internal Azure DevOps build (typically from `dnceng/internal`). This skill can be run from **any directory**, including inside a repo like dotnet/roslyn. The SDK is installed to a temp folder and validation runs in a separate temp folder, so nothing in the user's working directory is created, modified, or depended upon. This skill requires the **ADO MCP server** configured for the `dnceng` organization to be available in your session. ## How to Invoke This Skill In a copilot session with an ADO MCP server configured for the `dnceng` organization, ask something like: - "Install the .NET SDK from this build: https://dev.azure.com/dnceng/internal/_build/results?buildId=2919304" - "Install .NET SDK from ADO build 2919304" - "Use /validate-sdk to set up the SDK from build 2919304" ### Required Input The user must provide **one** of the following: - An **Azure DevOps build URL** from `dev.azure.com/dnceng/internal` containing a `buildId` query parameter - A **numeric build ID** (e.g., `2919304`) from the dnceng/internal project ### What Does NOT Work as Input - **SharePoint/OneNote links** (e.g., `microsoft.sharepoint.com/...`) — these are documentation pages, not build links. If the user provides one, ask them for the Azure DevOps build URL or build ID instead. - **GitHub links** — this skill is for Azure DevOps builds, not GitHub Actions. - **NuGet package versions** — this skill installs the full SDK, not individual packages. If the user doesn't have the build URL or ID, suggest they look for a link like: `https://dev.azure.com/dnceng/internal/_build/results?buildId=XXXXXXX` in their signoff document or validation instructions. ## Step 1: Get the Build ID Extract the `buildId` from the Azure DevOps URL. For example, from: `https://dev.azure.com/dnceng/internal/_build/results?buildId=2919304&view=artifacts` The build ID is `2919304`. ## Step 2: Get the SDK Version from the Build Use the ADO MCP tool `ado-pipelines_get_build_status` with `project: "internal"` and the `buildId` to retrieve the build report. The build number in the report contains the SDK version. Parse out the version portion (e.g., `11.0.100-preview.2.26154.117` from build number `20260305.1-11.0.100-preview.2.26154.117-304630`). The SDK version follows the pattern `X.Y.Z-preview.N.NNNNN.NNN` and appears between the date prefix and the trailing BAR build ID. ## Step 3: Install Using dotnet-install Script Download and run the official dotnet-install script with the exact SDK version. Install into a **temp folder** so there is no dependency on the user's working directory or any repo: ```powershell $sdkDir = "$env:TEMP\validate-sdk-dotnet" $installScript = "$env:TEMP\dotnet-install.ps1" Invoke-WebRequest -Uri "https://dot.net/v1/dotnet-install.ps1" -OutFile $installScript # Install the specific SDK version to a temp directory & $installScript -Version "" -InstallDir $sdkDir ``` The script will automatically try multiple feeds: - `https://builds.dotnet.microsoft.com/dotnet` (primary public feed) - `https://ci.dot.net/public` (CI public feed — internal preview builds are often available here) If both feeds return 404, the SDK may not yet be published. Check with the user. For Linux/macOS, use the bash version instead: ```bash sdkDir="/tmp/validate-sdk-dotnet" curl -fsSL https://dot.net/v1/dotnet-install.sh -o /tmp/dotnet-install.sh chmod +x /tmp/dotnet-install.sh /tmp/dotnet-install.sh --version --install-dir $sdkDir ``` ## Step 4: Verify Installation Run the installed dotnet to confirm: ```powershell & "$env:TEMP\validate-sdk-dotnet\dotnet.exe" --version ``` This should print the exact SDK version that was requested. **Troubleshooting:** If `dotnet.exe` is not found in the install directory, the dotnet host may not have been downloaded (the directory will only contain `host/`, `sdk/`, `shared/` subdirectories without a `dotnet.exe`). In this case, remove the directory and reinstall: ```powershell Remove-Item -Recurse -Force "$env:TEMP\validate-sdk-dotnet" -ErrorAction SilentlyContinue & $installScript -Version "" -InstallDir "$env:TEMP\validate-sdk-dotnet" ``` ## Step 5: Configure for Use The SDK is installed to a **temp directory**, not system-wide. This means `dotnet --list-sdks` using the system dotnet will NOT show it. This is by design — it avoids affecting the user's system .NET setup. To use the locally installed SDK: - Run directly: `$env:TEMP\validate-sdk-dotnet\dotnet.exe` - Or prepend to PATH for the current session: `$env:PATH = "$env:TEMP\validate-sdk-dotnet;$env:PATH"` ## Step 6: Validate with `#error version` Use a **file-based app** (a .NET 10+ feature) to extract compiler details. This **must** run in an isolated temp folder to avoid interference from `global.json`, `.sln`, or `.csproj` files in the user's working directory (e.g., a roslyn repo checkout). 1. Create a temp directory with `app.cs` and a pinned `global.json`. The `#:property` directive adds the internal preview feed so `dotnet run` can restore the runtime packs for a not-yet-public build. > **⚠️ The feed name must match the SDK's .NET major version.** The feed is named `dotnet` where `` is the major version of the SDK you installed. For an `11.0.x` SDK use `dotnet11`; for a `12.0.x` SDK use `dotnet12`; for a `10.0.x` SDK use `dotnet10`. **Do not hardcode `dotnet11`** — derive it from ``. Using the wrong feed will fail restore with `NU1102`. See the feed table at https://github.com/dotnet/dotnet/blob/main/docs/builds-table.md. ```powershell # Derive the feed name from the SDK major version so this works for any release (dotnet11, dotnet12, ...) $sdkMajor = ([version](("" -split '-')[0])).Major $feed = "https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet$sdkMajor/nuget/v3/index.json" $testDir = "$env:TEMP\validate-sdk-test" New-Item -ItemType Directory -Path $testDir -Force | Out-Null Set-Content -Path "$testDir\app.cs" -Value @" #:property RestoreAdditionalProjectSources=$feed #error version "@ # Pin the SDK version to prevent any parent global.json from overriding it Set-Content -Path "$testDir\global.json" -Value '{"sdk":{"version":"","allowPrerelease":true}}' ``` **Why the `#:property` feed matters:** For preview builds, the matching runtime packs (e.g. `Microsoft.NETCore.App.Runtime.*`) are often not yet on nuget.org, so `dotnet run` fails during restore with `NU1102: Unable to find package ...` before it ever compiles. Adding the internal preview feed via `RestoreAdditionalProjectSources` lets restore succeed. 2. Run the file-based app from the temp directory using the installed SDK. You **must `cd` into the temp directory** and set `DOTNET_MULTILEVEL_LOOKUP=0` to ensure full isolation from the user's environment: ```powershell Push-Location $testDir $env:DOTNET_MULTILEVEL_LOOKUP = "0" & "$env:TEMP\validate-sdk-dotnet\dotnet.exe" run app.cs 2>&1 | Select-String -Pattern "CS8304" Pop-Location ``` **Why this isolation matters:** Without `cd` + `global.json` + `DOTNET_MULTILEVEL_LOOKUP=0`, the dotnet CLI walks up the directory tree looking for `global.json`. If run from inside a repo like dotnet/roslyn, it would find the repo's `global.json` and try to use a different SDK version, causing the validation to fail or test the wrong compiler. 3. **The build is expected to fail** (exit code non-zero) because `#error version` is a deliberate compile error. The success criterion is seeing the `CS8304` diagnostic in the output. Look for the `CS8304` line which contains: - **Compiler version** (e.g., `5.6.0-2.26154.117`) - **Compiler commit SHA** in parentheses (e.g., `6dbf4ee311820b91535cc405fb9f72f3e1ec85fc`) - **Language version** (e.g., `preview`) 4. Clean up: ```powershell Remove-Item -Recurse -Force "$env:TEMP\validate-sdk-test" -ErrorAction SilentlyContinue ``` ## Step 7: Trace the Roslyn SHA The compiler commit SHA from Step 6 is a commit in the **dotnet/dotnet** VMR (Virtual Mono Repo), not dotnet/roslyn directly. 1. Look up the compiler SHA in dotnet/dotnet using `github-mcp-server-get_commit` (owner: `dotnet`, repo: `dotnet`). 2. Fetch `src/source-manifest.json` at that commit using `github-mcp-server-get_file_contents` (owner: `dotnet`, repo: `dotnet`, path: `src/source-manifest.json`, sha: ``). 3. In the JSON, find the entry with `"path": "roslyn"` and extract its `commitSha` — this is the actual dotnet/roslyn commit. 4. Look up that Roslyn SHA using `github-mcp-server-get_commit` (owner: `dotnet`, repo: `roslyn`) to get the commit summary and date. ## Step 8: Output Validation Report Output a report in this format: ``` ## .NET SDK Validation Report - **SDK Version:** `` - **Compiler Version:** `` - **dotnet/dotnet commit:** https://github.com/dotnet/dotnet/commit/ - **dotnet/roslyn commit:** https://github.com/dotnet/roslyn/commit/ **Last Roslyn commit:** "" by — merged . ``` Use full SHAs (not shortened) and plain URLs (not markdown link syntax). ## Notes - Build artifacts can also be explored via `ado-pipelines_get_build_log` and `ado-pipelines_get_build_log_by_id` if you need to inspect specific asset names. - The dotnet-install script approach is preferred over downloading artifacts directly, as the SDK zip is typically published to the CI feeds even for preview builds.