migrate-dotnet10-to-dotnet11
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,
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.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:
to:
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 dotnet10to11.md Always (applies to all .NET 11 projects)
references/sdk msbuild dotnet10to11.md Always (SDK and build tooling changes)
references/aspnetcore dotnet10to11.md Project uses ASP.NET Core (OpenAPI, Blazor)
references/efcore dotnet10to11.md Project uses Entity Framework Core
references/cryptography dotnet10to11.md Project uses cryptography APIs, mTLS, or targets macOS
references/runtime jit dotnet10to11.md Deploying to older hardware, embedded devices, or using NativeAOT
Work through each build error systematically. Common patterns:
1. C 15 Span collection expression safe context — Collection expressions of Span<T / ReadOnlySpan<T type now have declaration block safe context. Code assigning span collection expressions to variables in outer scopes will error. Use array type or move the expression to the correct scope.
2. ref readonly delegates/local functions need InAttribute — If synthesizing delegates from ref readonly returning methods or using ref readonly local functions, ensure System.Runtime.InteropServices.InAttribute is available.
3. nameof(this.) in attributes — Remove this. qualifier; use nameof(P) instead of nameof(this.P) .
4. with() in collection expressions (C 15) — with(...) is now treated as constructor arguments, not a method call. Use @with(...) to call a method named with .
5. Dynamic && / with interface operand — Interface types as left operand of && / with dynamic right operand now errors at compile time. Cast to concrete type or dynamic .
6. EF Core Cosmos sync I/O removal — ToList() , SaveChanges() , etc. on Cosmos provider always throw. Convert to async equivalents.
7. SYSLIB0063: NamedPipeClientStream isConnected parameter obsoleted — The constructor overload taking bool isConnected is obsoleted. Remove the isConnected argument and use the new 3 parameter constructor. Projects with TreatWarningsAsErrors will fail to build.
8. when switch expression arm parsing — (X.Y) when is now parsed as a constant pattern with a when clause instead of a cast expression, which can cause existing code to fail to compile or change meaning. Review switch expressions using when and adjust syntax as needed.
9. Microsoft.OpenApi v3 breaking changes — Microsoft.AspNetCore.OpenApi now depends on Microsoft.OpenApi 3.x. Code using Microsoft.OpenApi types directly ( OpenApiDocument , OpenApiSchema , etc.) will have compile errors. Follow the v3 upgrade guide.
10. EF Core Design package no longer transitive — Microsoft.EntityFrameworkCore.Tools and .Tasks no longer depend on .Design . Add an explicit PackageReference if needed.
11. EFOptimizeContext MSBuild property removed — Replace with <EFScaffoldModelStage and <EFPrecompileQueriesStage .
Step 4: Address behavioral changes
These changes compile successfully but alter runtime behavior. Review each one and determine impact:
1. DeflateStream/GZipStream empty payload — Now writes headers and footers even for empty payloads. If your code checks for zero length output, update the check.
2. MemoryStream maximum capacity — Maximum capacity updated and exception behavior changed. Review code that creates large MemoryStreams or relies on specific exception types.
3. TAR header checksum validation — TAR reading APIs now verify checksums. Corrupted or hand crafted TAR files may now fail to read.
4. ZipArchive.CreateAsync eager loading — ZipArchive.CreateAsync eagerly loads entries. May affect memory usage for large archives.
5. Environment.TickCount consistency — Made consistent with Windows timeout behavior. Code relying on specific tick count behavior may need adjustment.
6. DSA removed from macOS — DSA cryptographic operations throw on macOS. Use a different algorithm (RSA, ECDSA).
7. Japanese Calendar minimum date — Minimum supported date corrected. Code using very early Japanese Calendar dates may be affected.
8. Minimum hardware requirements — x86/x64 baseline moved to x86 64 v2 ; Windows Arm64 requires LSE . Verify deployment targets meet requirements.
9. Mono launch target for .NET Framework — No longer set automatically. If using Mono for .NET Framework apps on Linux, specify explicitly.
10. Unhandled BackgroundService exceptions stop the host — Exceptions from ExecuteAsync() now propagate and crash the host. Add try/catch in background services that should not bring down the application.
11. ZipArchive CRC32 validation — ZIP reads now validate CRC32 checksums. Corrupt or truncated archives that previously succeeded will now throw InvalidDataException .
12. TarWriter emits HardLink entries — Hard linked files are now written as HardLink entries instead of duplicated data. Consumers of .NET produced tar archives must handle HardLink entries.
13. AIA certificate downloads disabled — Server side client certificate validation no longer downloads intermediate CAs via AIA by default. Pre install the full chain or have clients send intermediates.
14. Blazor Virtualize OverscanCount default changed — Default OverscanCount changed from 3 to 15. Set explicitly if performance sensitive.
15. Microsoft.Data.SqlClient 7.0 — Entra ID auth separated — Azure/Entra ID authentication dependencies removed from the core SqlClient package. Add Microsoft.Data.SqlClient.Extensions.Azure if using Entra ID auth.
16. SqlVector<T> excluded from SELECT — Vector properties are no longer auto loaded. Use explicit projections to include vector values.
17. SQLitePCLRaw encryption bundles removed — bundle e sqlcipher and other encryption bundle packages removed in SQLitePCLRaw 3.0.
18. NativeAOT Unix native library lib prefix — Output filenames now include lib prefix on Linux/macOS (e.g., libMyLib.so ).
Step 5: Update infrastructure
1. Dockerfiles : Update base images from 10.0 to 11.0:
2. CI/CD pipelines : Update SDK version references. If using global.json , update the sdk.version in your existing file while preserving other keys (such as rollForward and test configuration):
3. Hardware deployment targets : Verify all deployment targets meet the updated minimum hardware requirements (x86 64 v2 for x86/x64, LSE for Windows Arm64).
Step 6: Verify
1. Run a full clean build: dotnet build no incremental
2. Run all tests: dotnet test
3. If the application is containerized, build and test the container image
4. Smoke test the application, paying special attention to:
Compression behavior with empty streams
TAR file reading (checksum validation and HardLink entries)
EF Core Cosmos DB operations (must be async)
DSA usage on macOS
Memory intensive MemoryStream usage
Span collection expression assignments
BackgroundService exception handling
mTLS / client certificate chain validation
EF Core SQL Server with Entra ID authentication
NativeAOT output filenames on Unix
5. Review the diff and ensure no unintended behavioral changes were introdu