README

C# Language Design Notes for 2025

Wed December 17, 2025

C# Language Design Meeting for December 17th, 2025

• Collection expression arguments parsing question
• Null-conditionals evaluating to a pointer type
• Triage
  • Top-Level Members
  • Using local declaration improvements

Wed Dec 10, 2025

C# Language Design Meeting for December 10th, 2025

• Collection expression arguments

Wed Nov 12, 2025

C# Language Design Meeting for November 12th, 2025

• Unsafe evolution

Wed Nov 5, 2025

C# Language Design Meeting for November 5th, 2025

• Unsafe evolution

Wed Oct 29, 2025

C# Language Design Meeting for October 29th, 2025

• Unsafe evolution

Mon Oct 13, 2025

C# Language Design Meeting for October 13th, 2025

• Collection expression safe-context bug fix
• Immediately-enumerated collection expressions

Wed Oct 1, 2025

C# Language Design Meeting for October 1st, 2025

• Closed enums
• Closed Hierarchies

Mon Sep 29, 2025

C# Language Design Meeting for September 29th, 2025

• Union Syntax Thunderdome Part 2
• Enums vs Unions

Wed Sep 24, 2025

C# Language Design Meeting for September 24th, 2025

• Union Syntax Thunderdome Part 1

Wed Sep 17, 2025

C# Language Design Meeting for September 17th, 2025

• Unsafe evolution

Wed Sep 10, 2025

C# Language Design Meeting for September 10th, 2025

• Unions overview

Wed Aug 27, 2025

C# Language Design Meeting for August 27th, 2025

• Type inference in patterns
• Type value conversion
• Union syntax

Wed Aug 20, 2025

C# Language Design Meeting for August 20th, 2025

• Union interfaces
• Target-type inference improvements

Mon Aug 18, 2025

C# Language Design Meeting for August 18th, 2025

• C# 15 Kickoff and Themes
  • Unions
  • Extensions
  • Dictionary expressions
  • Type inference
  • Continuing the null monad
  • Object initialization
  • Top-level methods
  • Caller type name
  • Switch statement/expression improvements

Wed Aug 13, 2025

C# Language Design Meeting for August 13th, 2025

• Unions

Wed Jul 30, 2025

C# Language Design Meeting for July 30th, 2025

• '/main' and top-level statements
• Union proposals overview
• Add type parameter restriction to closed hierarchies
• Standard unions
• Union interfaces
• Custom unions
• Non-boxing access pattern

Mon Jun 30, 2025

C# Language Design Meeting for June 30th, 2025

• Type parameter inference from constraints
• Target-typed static member lookup

Wed Jun 25, 2025

C# Language Design Meeting for June 25th, 2025

• Unions
  • Stand-alone issues
  • Mutually exclusive issues

Mon Jun 23, 2025

C# Language Design Meeting for June 23rd, 2025

• Extensions
  • Use of extension operators in LINQ expression trees
  • ref encoding and conflict checks
  • Extern support
  • Lookup

Wed Jun 18, 2025

C# Language Design Meeting for June 18th, 2025

• Iterators in lambdas
• Extensions

Wed Jun 11, 2025

C# Language Design Meeting for June 11th, 2025

• Extensions
  • Dynamic resolution of operator true/false
  • Extension operators in LINQ expression trees
  • Built-in operator protection rules
  • Extension module initializers
  • Extension methods as entry points
  • Langversion behavior for new extensions
  • nameof

Mon Jun 9, 2025

C# Language Design Meeting for June 9th, 2025

• Extensions - crefs

Wed Jun 4, 2025

C# Language Design Meeting for June 4th, 2025

• Extensions
  • Should extension operators on nullable of extended type be disallowed
  • Applicability of bitwise operators during evaluation of user-defined conditional logical operators
  • Extension user-defined conditional logical operators
  • Extension compound assignment operators
  • Delegate returning properties
  • Extension declaration validation
  • Cref references

Wed May 28, 2025

C# Language Design Meeting for May 28th, 2025

• Nominal type unions

Mon May 12, 2025

C# Language Design Meeting for May 12th, 2025

• Collection expression arguments
  • Empty argument lists
  • Constructor binding behavior
  • Syntax
• Dictionary expressions

Wed May 7, 2025

C# Language Design Meeting for May 7th, 2025

• Collection Expression Arguments
  • Interface target type
  • Constructor binding behavior
  • Syntax

Mon May 5, 2025

C# Language Design Meeting for May 5th, 2025

• Extensions
  • XML Docs
  • Participation in pattern-based constructs
  • Skeleton type metadata
  • Single-phase consequences

Wed, Apr 23, 2025

C# Language Design Meeting for April 23rd, 2025

• Extensions
  • Extension operators
  • Overload resolution priority
• Dictionary Expressions

Wed Apr 16, 2025

C# Language Design Meeting for April 16th, 2025

• Extensions

Mon Apr 14, 2025

C# Language Design Meeting for April 14th, 2025

• Dictionary expressions
• Collection expression arguments

Wed Apr 9, 2025

C# Language Design Meeting for April 9th, 2025

• Dictionary expressions
• Collection expression arguments

Mon Apr 7, 2025

C# Language Design Meeting for April 7th, 2025

• Breaking change discussion: making partial members in interfaces virtual and/or public
• Interpolated string handler argument values

April 2, 2025

C# Language Design Meeting for April 2nd, 2025

• User Defined Compound Assignment Operators
  • Should readonly modifier be allowed in structures?
  • Should shadowing be allowed
  • Should we have any consistency enforcement between declared += and + operators?
• Readonly setters
  • Expansions

Mon Mar 24, 2025

C# Language Design Meeting for March 24th, 2025

• Dictionary Expressions
  • Support dictionary types as params type
  • Type inference for KeyValuePair<K, V> collections
  • Overload resolution for KeyValuePair<K, V> collections
• Extensions
  • Signature conflict rules
  • extension vs extensions

Wed Mar 19, 2025

C# Language Design Meeting for March 19th, 2025

• Readonly setters on non-variables

Mon Mar 17, 2025

C# Language Design Meeting for March 17th, 2025

• Collection expression arguments
  • with breaking change
  • Collection expression arguments and conversions
• Dictionary expressions
• Extensions
  • Accessibility
  • Static factory scenarios

Mon Mar 12, 2025

C# Language Design Meeting for March 12th, 2025

• Optional and named parameters in expression trees
• Collection builder method parameter order
• Ignored directives

Mon Mar 10, 2025

C# Language Design Meeting for March 10th, 2025

• Extensions
  • Property method calling
  • Scoping and Shadowing
  • Type parameter inferrability
  • Accessibility

Wed Mar 5, 2025

C# Language Design Meeting for March 5th, 2025

• Dictionary expressions
• Target-typed static member lookup

Mon Mar 3, 2025

C# Language Design Meeting for March 3rd, 2025

• Extensions

Wed Feb 26, 2025

C# Language Design Meeting for February 26th, 2025

• Extensions

Mon Feb 24, 2025

C# Language Design Meeting for February 24th, 2025

• Extensions
• Interpolated string handler method names

Wed Feb 19, 2025

C# Language Design Meeting for February 19th, 2025

• Extensions

Wed Feb 12, 2025

C# Language Design Meeting for February 12th, 2025

• User-defined instance-based operators
• Left-right join in query expressions

Wed Jan 22, 2025

C# Language Design Meeting for January 22nd, 2025

• Partial events and constructors
• Collection expression arguments
• Extensions disambiguation syntax

Wed Jan 15, 2025

C# Language Design Meeting for January 15th, 2025

• fieldof
• Simple lambda parameters
• Interpolated string handler method names

Mon Jan 13th, 2025

C# Language Design Meeting for January 13th, 2025

• Discriminated Unions

Mon Jan 6, 2025

C# Language Design Meeting for January 6th, 2025

• Ignoring ref structs in Expressions
• Extensions