Breaking changes in .NET 10

If you're migrating an app to .NET 10, the breaking changes listed here might affect you. Changes are grouped by technology area, such as ASP.NET Core or Windows Forms.

[!INCLUDE binary-source-behavioral]

Note

This article is a work in progress. It's not a complete list of breaking changes in .NET 10.

ASP.NET Core

Title	Type of change	Introduced version
Cookie login redirects disabled for known API endpoints	Behavioral change	Preview 7
Deprecation of WithOpenApi extension method	Source incompatible	Preview 7
Exception diagnostics suppressed when TryHandleAsync returns true	Behavioral change	Preview 7
IActionContextAccessor and ActionContextAccessor are obsolete	Source incompatible/behavioral change	Preview 7
IncludeOpenAPIAnalyzers property and MVC API analyzers are deprecated	Source incompatible	Preview 7
IPNetwork and ForwardedHeadersOptions.KnownNetworks are obsolete	Source incompatible	Preview 7
Microsoft.Extensions.ApiDescription.Client package deprecated	Source incompatible	Preview 7
Razor run-time compilation is obsolete	Source incompatible	Preview 7
WebHostBuilder, IWebHost, and WebHost are obsolete	Source incompatible	RC 1

Containers

Title	Type of change	Introduced version
Default .NET images use Ubuntu	Behavioral change	Preview 1

Core .NET libraries

Title	Type of change	Introduced version
ActivitySource.CreateActivity and ActivitySource.StartActivity behavior change	Behavioral change	Preview 1
Arm64 SVE nonfaulting loads require mask	Binary/source incompatible	Preview 1
BufferedStream.WriteByte no longer performs implicit flush	Behavioral change	Preview 4
C# 14 overload resolution with span parameters	Behavioral change	Preview 1
Consistent shift behavior in generic math	Behavioral change	Preview 1
Default trace context propagator updated to W3C standard	Behavioral change	Preview 4
DriveInfo.DriveFormat returns Linux filesystem types	Behavioral change	Preview 6
DynamicallyAccessedMembers annotation removed from DefaultValueAttribute ctor	Binary/source incompatible	Preview 7
Explicit struct Size disallowed with InlineArray	Binary incompatible	Preview 7
FilePatternMatch.Stem changed to non-nullable	Source incompatible/behavioral change	RC 1
GnuTarEntry and PaxTarEntry no longer includes atime and ctime by default	Behavioral change	Preview 5
LDAP DirectoryControl parsing is now more stringent	Behavioral change	Preview 1
MacCatalyst version normalization	Behavioral change	Preview 1
.NET runtime no longer provides default termination signal handlers	Behavioral change	Preview 5
System.Linq.AsyncEnumerable included in core libraries	Source incompatible	Preview 1
Type.MakeGenericSignatureType argument validation	Behavioral change	Preview 3
YMM embedded rounding removed from AVX10.2	Behavioral change	Preview 5

Cryptography

Title	Type of change	Introduced version
CoseSigner.Key can be null	Behavioral/source incompatible change	Preview 7
MLDsa and SlhDsa 'SecretKey' members renamed	Source incompatible	RC 1
OpenSSL cryptographic primitives aren't supported on macOS	Behavioral change	Preview 6
X500DistinguishedName validation is stricter	Behavioral change	Preview 1
X509Certificate and PublicKey key parameters can be null	Behavioral/source incompatible change	Preview 3
Environment variable renamed to DOTNET_OPENSSL_VERSION_OVERRIDE	Behavioral change	Preview 1

Entity Framework Core

Breaking changes in EF Core 10

Extensions

Title	Type of change	Introduced version
BackgroundService runs all of ExecuteAsync as a Task	Behavioral change	Preview 1
Null values preserved in configuration	Behavioral change	Preview 7
Message no longer duplicated in Console log output	Behavioral change	Preview 7
ProviderAliasAttribute moved to Microsoft.Extensions.Logging.Abstractions assembly	Source incompatible	Preview 4
Removed DynamicallyAccessedMembers annotation from trim-unsafe Microsoft.Extensions.Configuration code	Binary incompatible	Preview 6

Globalization

Title	Type of change	Introduced version
Environment variable renamed to DOTNET_ICU_VERSION_OVERRIDE	Behavioral change	Preview 1

Interop

Title	Type of change	Introduced version
Single-file apps no longer look for native libraries in executable directory	Behavioral change	Preview 6
Specifying DllImportSearchPath.AssemblyDirectory only searches the assembly directory	Behavioral change	Preview 5

Networking

Title	Type of change	Introduced version
HTTP/3 support disabled by default with PublishTrimmed	Source incompatible	Preview 6
Streaming HTTP responses enabled by default in browser HTTP clients	Behavioral change	Preview 3
`Uri` length limits removed	Behavioral change	Preview 7

SDK and MSBuild

Title	Type of change	Introduced version
.NET CLI `--interactive` defaults to `true` in user scenarios	Behavioral change	Preview 3
`dotnet` CLI commands log non-command-relevant data to stderr	Behavioral change	RC 2
.NET tool packaging creates RuntimeIdentifier-specific tool packages	Behavioral change	Preview 6
Default workload configuration from 'loose manifests' to 'workload sets' mode	Behavioral change	Preview 2
dnx.ps1 file is no longer included in .NET SDK	Source incompatible	GA
`dotnet new sln` defaults to SLNX file format	Behavioral change	RC 1
`dotnet package list` performs restore	Behavioral change	Preview 4
`dotnet restore` audits transitive packages	Behavioral change	Preview 3
`dotnet tool install --local` creates manifest by default	Behavioral change	Preview 7
`dotnet watch` logs to stderr instead of stdout	Behavioral change	RC 2
project.json not supported in `dotnet restore`	Source incompatible	Preview 7
SHA-1 fingerprint support deprecated in `dotnet nuget sign`	Behavioral change	Preview 1
MSBUILDCUSTOMBUILDEVENTWARNING escape hatch removed	Behavioral change	Preview 1
MSBuild custom culture resource handling	Behavioral change	Preview 1
NU1510 is raised for direct references pruned by NuGet	Source incompatible	Preview 1
NuGet packages with no runtime assets aren't included in deps.json	Source incompatible	Preview 5
PackageReference without a version raises an error	Behavioral change	Preview 6
PrunePackageReference privatizes direct prunable references	Behavioral change	Preview 7
Version requirements for .NET 10 SDK	Behavioral change	RC 2
HTTP warnings promoted to errors in `dotnet package list` and `dotnet package search`	Behavioral/source incompatible change	Preview 4
NUGET_ENABLE_ENHANCED_HTTP_RETRY environment variable removed	Behavioral change	Preview 6
NuGet logs an error for invalid package IDs	Behavioral change	RC 1

Serialization

Title	Type of change	Introduced version
XmlSerializer no longer ignores properties marked with ObsoleteAttribute	Behavioral change	Preview 1

Windows Forms

Title	Type of change	Introduced version
API obsoletions	Source incompatible	Preview 1
Applications referencing both WPF and WinForms must disambiguate MenuItem and ContextMenu types	Source incompatible	Preview 1
Renamed parameter in HtmlElement.InsertAdjacentElement	Source incompatible	Preview 1
TreeView checkbox image truncation	Behavioral change	Preview 1
StatusStrip uses System RenderMode by default	Behavioral change	Preview 1
System.Drawing OutOfMemoryException changed to ExternalException	Behavioral change	Preview 5

Windows Presentation Foundation (WPF)

Title	Type of change	Introduced version
Empty ColumnDefinitions and RowDefinitions are disallowed	Source incompatible	Preview 5
Incorrect usage of DynamicResource causes application crash	Source incompatible/behavioral change	Preview 4

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