migrate-dotnet8-to-dotnet9 SKILL.md skillA
migrate-dotnet8-to-dotnet9 from dotnet/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add dotnet/skills/migrate-dotnet8-to-dotnet9@git:20260421.05aeb65Pins git:20260421.05aeb65 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- dotnet/skills
- Path
plugins/dotnet-upgrade/skills/migrate-dotnet8-to-dotnet9/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260421.05aeb65, committed Apr 21, 2026
- First version recorded
- Mar 11, 2026
- Size
- 15,769 bytes
- Repository stars
- 5,836
- License
- MIT
Migrate a .NET 8 project to .NET 9 and resolve all breaking changes. USE FOR: upgrading TargetFramework from net8.0 to net9.0, fixing build errors after updating the .NET 9 SDK, resolving behavioral changes in .NET 9 / C# 13 / ASP.NET Core 9 / EF Core 9, replacing BinaryFormatter (now always throws), resolving SYSLIB0054-SYSLIB0057, adapting to params span overload resolution, fixing C# 13 compiler changes, updating HttpClientFactory for SocketsHttpHandler, and resolving EF Core 9…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# .NET 8 → .NET 9 Migration Migrate a .NET 8 project or solution to .NET 9, systematically resolving all breaking changes. The outcome is a project targeting `net9.0` that builds cleanly, passes tests, and accounts for every behavioral, source-incompatible, and binary-incompatible change introduced in the .NET 9 release. ## When to Use - Upgrading `TargetFramework` from `net8.0` to `net9.0` - Resolving build errors or new warnings after updating the .NET 9 SDK - Adapting to behavioral changes in .NET 9 runtime, ASP.NET Core 9, or EF Core 9 - Replacing `BinaryFormatter` usage (now always throws at runtime) - Updating CI/CD pipelines, Dockerfiles, or deployment scripts for .NET 9 ## When Not to Use - The project already targets `net9.0` and builds cleanly — migration is done. If the goal is to reach `net10.0`, use the `migrate-dotnet9-to-dotnet10` skill as the next step. - Upgrading from .NET 7 or earlier — address the prior version breaking changes first - Migrating from .NET Framework — that is a separate, larger effort - Greenfield projects that start on .NET 9 (no migration needed) ## Inputs | Input | Required | Description | |-------|----------|-------------| …
Read the whole file at its exact version.
How to install
mdr add dotnet/skills/migrate-dotnet8-to-dotnet9@sha256:95d6de4776ccd6b8The line at the top of this page pins the label git:20260421.05aeb65, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_6llo4kec4tzhm6j3)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between Mar 11, 2026 and Apr 21, 2026, about one every 41 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260421.05aeb65 latest | 2026-04-21 | 05aeb65 | 15,769 B | A | view · diff |
| git:20260311.e9370fe | 2026-03-11 | e9370fe | 15,756 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (15769 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
dotnet/skills · 5,836 stars · license MIT · pushed 2026-11-06 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_6llo4kec4tzhm6j3 GET https://markdownregistry.com/api/v1/resolve?ref=dotnet/skills/migrate-dotnet8-to-dotnet9 GET https://markdownregistry.com/api/v1/blob/95d6de4776ccd6b8a71bf1ce776eb3cd8ddb67b590ce1ca66db4785a2d91d9a8
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.