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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.

This article categorizes each breaking change as binary incompatible or source incompatible, or as a behavioral change:

  • Binary incompatible - When run against the new runtime or component, existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.

  • Source incompatible - When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.

  • Behavioral change - Existing code and binaries may behave differently at runtime. If the new behavior is undesirable, existing code would need to be updated and recompiled.

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Razor runtime compilation is obsolete Source incompatible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

Containers

Title Type of change
Default .NET images use Ubuntu Behavioral change

Core .NET libraries

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

Cryptography

Title Type of change
CompositeMLDsa updated to draft-08 Behavioral change
CoseSigner.Key can be null Behavioral/source incompatible change
MLDsa and SlhDsa 'SecretKey' members renamed Source incompatible
OpenSSL cryptographic primitives aren't supported on macOS Behavioral change
OpenSSL 1.1.1 or later required on Unix Behavioral change
X500DistinguishedName validation is stricter Behavioral change
X509Certificate and PublicKey key parameters can be null Behavioral/source incompatible change
Environment variable renamed to DOTNET_OPENSSL_VERSION_OVERRIDE Behavioral change

Entity Framework Core

Breaking changes in EF Core 10

Extensions

Title Type of change
BackgroundService runs all of ExecuteAsync as a Task Behavioral change
Fix issues in GetKeyedService() and GetKeyedServices() with AnyKey Behavioral change
Null values preserved in configuration Behavioral change
Message no longer duplicated in Console log output Behavioral change
ProviderAliasAttribute moved to Microsoft.Extensions.Logging.Abstractions assembly Source incompatible
Removed DynamicallyAccessedMembers annotation from trim-unsafe Microsoft.Extensions.Configuration code Binary incompatible

Globalization

Title Type of change
Environment variable renamed to DOTNET_ICU_VERSION_OVERRIDE Behavioral change

Install tool

Title Type of change
dotnet.acquire API for VS Code no longer always downloads latest Behavioral change

Interop

Title Type of change
Casting IDispatchEx COM object to IReflect fails Behavioral change
Single-file apps no longer look for native libraries in executable directory Behavioral change
Specifying DllImportSearchPath.AssemblyDirectory only searches the assembly directory Behavioral change

Networking

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

Reflection

Title Type of change Introduced version
More restricted annotations on InvokeMember/FindMembers/DeclaredMembers Behavioral/source incompatible

SDK and MSBuild

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

Serialization

Title Type of change
System.Text.Json checks for property name conflicts Behavioral change
XmlSerializer no longer ignores properties marked with ObsoleteAttribute Behavioral change

Windows Forms

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

Windows Presentation Foundation (WPF)

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