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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 run time. 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 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Razor run-time compilation is obsolete Source incompatible Preview 7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