.NET docs: What's new for .NET 9

This article lists some of the major changes to docs for .NET 9.

.NET security

Updated articles

• Cross-Platform Cryptography in .NET - Crypto docs

.NET breaking changes

New articles

• Breaking changes in .NET 9
• dotnet workload commands output change
• GetXmlNamespaceMaps type change
• installer repo version no longer included in productcommits files
• API obsoletions with non-default diagnostic IDs (.NET 9)
• BindingSource.SortDescriptions doesn't return null
• Breaking changes in .NET 9
• Changes to nullability annotations (Windows Forms)
• ComponentDesigner.Initialize throws ArgumentNullException
• Creating type of array of System.Void not allowed
• DataGridViewRowAccessibleObject.Name starting row index
• Default Equals() and GetHashCode() throw for types marked with InlineArrayAttribute
• DefaultKeyResolution.ShouldGenerateNewKey has altered meaning
• Deprecated desktop Windows/macOS/Linux MonoVM runtime packages
• Floating point-to-integer conversions are saturating
• HttpListenerRequest.UserAgent is nullable
• In-box BinaryFormatter implementation removed and always throws
• Inline array struct size limit is enforced
• InMemoryDirectoryInfo prepends rootDir to files
• No exception if DataGridView is null
• PictureBox raises HttpClient exceptions
• RuntimeHelpers.GetSubArray returns different type
• Support for empty environment variables
• Terminal logger is default
• Warning emitted for .NET Standard 1.x targets

.NET fundamentals

New articles

• CA2022: Avoid inexact read with Stream.Read
• CA2265: Do not compare Span<T> to null or default
• Configuration source generator

Updated articles

• .NET Standard
• Code quality rules
• Configuration in .NET - Add content for config source gen with interceptors
• Obsolete features in .NET 5+ - Update diagnostic docs for SYSLIB0009
• Overview of .NET source code analysis
• Synchronizing data for multithreading - Add language reference for lock
• SYSLIB0009: AuthenticationManager is not supported - Update diagnostic docs for SYSLIB0009
• What's new in the SDK and tooling for .NET 9

C# language

New articles

• Errors and warnings associated with ref struct types
• Errors and warnings related to partial type and partial member declarations
• Errors and warnings related to the lock statement and thread synchronization
• Errors and warnings related to the params modifier on method parameters
• Errors and warnings related to the yield return statement and iterator methods
• Partial member (C# Reference)
• Resolve errors and warnings that affect overload resolution.
• What's new in C# 13

Updated articles

• interface (C# Reference) - Add reference and conceptual content for ref struct allowed in interfaces
• ref structure types (C# reference)
  • Add reference and conceptual content for ref struct allowed in interfaces
  • Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Access Modifiers (C# Programming Guide) - Add conceptual content for partial properties
• Arithmetic operators (C# reference) - Explain better conversion from collection expression
• Assembly level attributes interpreted by the C# compiler - Add reference and conceptual content for ref struct allowed in interfaces
• Attributes - Add conceptual content for partial properties
• Automatically implemented properties - Add conceptual content for partial properties
• await operator - asynchronously await for a task to complete - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• C# Compiler Errors - Add errors and warnings for params arrays
• C# Keywords
  • Add conceptual content for partial properties
  • Add reference and conceptual content for ref struct allowed in interfaces
• C# Warning waves - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Collection expressions - C# language reference - Explain better conversion from collection expression
• Compiler Error CS0401 - Add, update compiler error and warning messages for ref struct interfaces
• Compiler Error CS1996 - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Compiler Error CS4004 - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Compiler Error CS8177 - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Constraints on type parameters (C# Programming Guide) - Add reference and conceptual content for ref struct allowed in interfaces
• default value expressions - produce the default value - Explain better conversion from collection expression
• Errors and warnings associated with ref struct types
  • Add new diagnostics
  • Add, update compiler error and warning messages for ref struct interfaces
• Errors and warnings associated with reference parameters, variables, and returns
  • Add new diagnostics
  • Add, update compiler error and warning messages for ref struct interfaces
• Errors and warnings related to the yield return statement and iterator methods
  • Add errors and warnings related to partial properties and indexers
  • update and consolidate errors related to iterators and yield
• Expression Trees - Add conceptual content for partial properties
• from clause (C# Reference) - Add conceptual content for partial properties
• get (C# Reference) - Add conceptual content for partial properties
• How to handle an exception using try/catch - Add conceptual content for partial properties
• How to initialize a dictionary with a collection initializer (C# Programming Guide) - Add params collections
• How to initialize objects by using an object initializer (C# Programming Guide) - Add params collections
• Indexers - Add conceptual content for partial properties
• Indexers in Interfaces (C# Programming Guide) - Add conceptual content for partial properties
• Interface Properties (C# Programming Guide) - Add conceptual content for partial properties
• Introduction to classes - Add conceptual content for partial properties
• Lambda expressions and anonymous functions - Add params collections
• Member access operators and expressions - the dot, indexer, and invocation operators.
  • Explain better conversion from collection expression
  • Add C# 13 small fixes
• Method Parameters
  • Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
  • Add params collections
• Methods in C# - Add params collections
• Miscellaneous attributes interpreted by the C# compiler
  • Add OverloadResolutionPriority conceptual documentation.
  • Add reference and conceptual content for ref struct allowed in interfaces
• nameof expression (C# reference) - Explain better conversion from collection expression
• new operator - The new operator creates a new instance of a type - Explain better conversion from collection expression
• Object and Collection Initializers (C# Programming Guide) - Add params collections
• Partial Classes and Methods (C# Programming Guide) - Add conceptual content for partial properties
• Partial type (C# Reference) - Add conceptual content for partial properties
• Properties (C# Programming Guide) - Add conceptual content for partial properties
• Recommended XML tags for C# documentation comments - Add conceptual content for partial properties
• Resolve errors and warnings generated from expressions prohibited in expression trees
  • Add conceptual content for partial properties
  • Add errors and warnings for params arrays
• Resolve errors and warnings in array and collection declarations and initialization expressions - Add errors and warnings related to overload resolution
• Resolve errors and warnings with inline array declarations
  • Add new diagnostics
  • Add conceptual content for partial properties
• Resolve warnings related to language features and versions
  • Add new diagnostics
  • Add, update compiler error and warning messages for ref struct interfaces
• Roadmap for Java developers learning C# - Add conceptual content for partial properties
• select clause (C# Reference) - Add conceptual content for partial properties
• set (C# Reference) - Add conceptual content for partial properties
• Standard .NET event patterns - Add conceptual content for partial properties
• The ref keyword - Add, update compiler error and warning messages for ref struct interfaces
• The C# type system - Add conceptual content for partial properties
• The checked and unchecked statements (C# reference) - Explain better conversion from collection expression
• The history of C# - Add conceptual content for partial properties
• The lock statement - ensure exclusive access to a shared resource - Add language reference for lock
• Type-testing operators and cast expressions - is, as, typeof and casts - Explain better conversion from collection expression
• Use string interpolation to construct formatted strings - Add conceptual content for partial properties
• Using indexers (C# Programming Guide) - Add conceptual content for partial properties
• Using Properties (C# Programming Guide) - Add conceptual content for partial properties
• where (generic type constraint) (C# Reference) - Add reference and conceptual content for ref struct allowed in interfaces
• yield statement - provide the next element - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Compiler Errors on partial type and member declarations - Add conceptual content for partial properties
• Errors and warnings for iterator methods and yield return - Add information for C# 13 feature ref locals and unsafe contexts in iterators and async methods
• Errors and warnings related to params arrays - Add params collections

.NET Framework

Updated articles

• Add Business Logic By Using Partial Methods - Add conceptual content for partial properties
• dangerousThreadingAPI MDA - Add language reference for lock