/migrate-dotnet10-to-dotnet11

name: migrate-dotnet10-to-dotnet11
description: >
  Migrate a .NET 10 project or solution to .NET 11 and resolve all breaking changes.
  This is a MIGRATION skill — use it when upgrading from .NET 10 to .NET 11,
  NOT for writing new programs.
  USE FOR: upgrading TargetFramework from net10.0 to net11.0, fixing build errors
  after updating the .NET 11 SDK, resolving source-breaking and behavioral changes
  in .NET 11 runtime, C# 15 compiler, and EF Core 11, adapting to updated minimum
  hardware requirements (x86-64-v2, Arm64 LSE), and updating CI/CD pipelines and
  Dockerfiles for .NET 11.
  DO NOT USE FOR: .NET Framework migrations, upgrading from .NET 9 or earlier,
  greenfield .NET 11 projects, or cosmetic modernization unrelated to the upgrade.
  NOTE: .NET 11 is in preview. Covers breaking changes through Preview 3.
license: MIT

.NET 10 → .NET 11 Migration

Migrate a .NET 10 project or solution to .NET 11, systematically resolving all breaking changes. The outcome is a project targeting `net11.0` that builds cleanly, passes tests, and accounts for every behavioral, source-incompatible, and binary-incompatible change introduced in .NET 11.

> **Note:** .NET 11 is currently in preview. This skill covers breaking changes documented through Preview 3.

When to Use

• Upgrading `TargetFramework` from `net10.0` to `net11.0`
• Resolving build errors or new warnings after updating the .NET 11 SDK
• Adapting to behavioral changes in .NET 11 runtime, ASP.NET Core 11, or EF Core 11
• Updating CI/CD pipelines, Dockerfiles, or deployment scripts for .NET 11
• Fixing C# 15 compiler breaking changes after SDK upgrade

When Not to Use

• The project already targets `net11.0` and builds cleanly — migration is done
• Upgrading from .NET 9 or earlier — address the .NET 9→10 breaking changes first
• Migrating from .NET Framework — that is a separate, larger effort
• Greenfield projects that start on .NET 11 (no migration needed)

Inputs

| Input | Required | Description | |-------|----------|-------------| | Project or solution path | Yes | The `.csproj`, `.sln`, or `.slnx` entry point to migrate | | Build command | No | How to build (e.g., `dotnet build`, a repo build script). Auto-detect if not provided | | Test command | No | How to run tests (e.g., `dotnet test`). Auto-detect if not provided | | Project type hints | No | Whether the project uses ASP.NET Core, EF Core, Cosmos DB, etc. Auto-detect from PackageReferences and SDK attributes if not provided |

Workflow

> **Answer directly from the loaded reference documents for information about .NET 11 breaking changes.** You may inspect the local repository (project/solution files, source code, configuration, build/test scripts) as needed to determine which changes apply. Do not fetch web pages or other external sources for breaking change information — the loaded references are the authoritative source. Focus on identifying which breaking changes apply and providing concrete fixes. > > **Commit strategy:** Commit at each logical boundary — after updating the TFM (Step 2), after resolving build errors (Step 3), after addressing behavioral changes (Step 4), and after updating infrastructure (Step 5). This keeps each commit focused and reviewable.

Step 1: Assess the project

1. Identify how the project is built and tested. Look for build scripts, `.sln`/`.slnx` files, or individual `.csproj` files. 2. Run `dotnet --version` to confirm the .NET 11 SDK is installed. If it is not, stop and inform the user. 3. Determine which technology areas the project uses by examining:

• **SDK attribute**: `Microsoft.NET.Sdk.Web` → ASP.NET Core; `Microsoft.NET.Sdk.WindowsDesktop` with `<UseWPF>` or `<UseWindowsForms>` → WPF/WinForms
• **PackageReferences**: `Microsoft.EntityFrameworkCore.*` → EF Core; `Microsoft.EntityFrameworkCore.Cosmos` → Cosmos DB provider
• **Dockerfile presence** → Container changes relevant
• **Cryptography API usage** → DSA on macOS affected; AIA cert download changes relevant
• **Compression API usage** → DeflateStream/GZipStream/ZipArchive changes relevant
• **TAR API usage** → Header checksum validation and HardLink entry changes relevant
• **`NamedPipeClientStream` usage with `SafePipeHandle`** → SYSLIB0063 constructor obsoletion relevant
• **`BackgroundService` usage** → Unhandled exceptions now stop the host
• **`Microsoft.OpenApi` direct usage** → v3 API breaking changes in ASP.NET Core OpenAPI
• **EF Core SQL Server with Entra ID auth** → SqlClient 7.0 auth dependency changes
• **NativeAOT native libraries on Unix** → Output filename prefix changed

4. Record which reference documents are relevant (see the reference loading table in Step 3). 5. Do a **clean build** (`dotnet build --no-incremental` or delete `bin`/`obj`) on the current `net10.0` target to establish a clean baseline. Record any pre-existing warnings.

Step 2: Update the Target Framework

1. In each `.csproj` (or `Directory.Build.props` if centralized), change:

   <TargetFramework>net10.0</TargetFramework>

to:

   <TargetFramework>net11.0</TargetFramework>

For multi-targeted projects, add `net11.0` to `<TargetFrameworks>` or replace `net10.0`.

2. Update all `Microsoft.Extensions.*`, `Microsoft.AspNetCore.*`, `Microsoft.EntityFrameworkCore.*`, and other Microsoft package references to their 11.0.x versions. If using Central Package Management (`Directory.Packages.props`), update versions there.

3. Run `dotnet restore`. Fix any restore errors before continuing.

4. Run `dotnet build`. Capture all errors and warnings — these will be addressed in Step 3.

Step 3: Fix source-breaking and compilation changes

Load reference documents based on the project's technology areas:

| Reference file | When to load | |----------------|-------------| | `references/csharp-compiler-dotnet10to11.md` | Always (C# 15 compiler breaking changes) | | `references/core-libraries-dotnet10to