C# Evolution

Without promising exact timelines for individual features, our goal is to try and support all new C# language changes introduced by Microsoft for the closest upcoming release after they have been finalized, often before and sometimes shortly after they have shipped in Visual C#. Of course details depend on the timelines for both Microsoft's releases and ours.

The lists below are kept in sync with this overview on the Roslyn GitHub page. We are currently looking at adding support for the new C# 7.x and 8.0 language features planned and proposed by Microsoft.

Planned for C# 8.0 (Microsoft-side status in parenthesis)

• Default Interface Methods – already implemented for all languages in v10.
• Nullable reference type (Preview 1) (#82380)
• Recursive Patterns (Preview 1)
• Async streams (Preview 1)
• Caller expression attribute (Prototype)
• Target-typed new (Prototype)
• Enhanced Using (Preview 1) (#82381)
• Generic attributes (In Progress)
• Ranges (Preview 1) (#82382)
• Default in deconstruction (Preview 3)
• Relax ordering of ref and partial modifiers (In Progress)
• Null-coalescing Assignment (Preview 1) – done
• Alternative interpolated verbatim strings (Confirmed) (#82383)
• stackalloc in nested contexts (In Progress)
• Unmanaged generic structs (Preview 1) (#82384)
• Local static functions (Preview 2) done
• Readonly members (Preview 2) (#82385)

Added for C# 7.3

• blittable — done .2299
• Support == and != for tuples — done .2299
• strongname
• Attribute on backing field — done .2299
• Ref Reassignment — done .2299
• Constraints — done .2299
• Stackalloc initializers
• Custom fixed
• Indexing movable fixed buffers
• Improved overload candidates
• Expression variables

C# 7.2

• ref readonly — done .2297
• interior pointer
• non-trailing named arguments — done .2299
• private protected — done, v10
• Conditional ref operator — done .2299
• Digit separator after base specifier
• ref and this ordering in ref extension

• Tiebreaker for by-val and in overloads

• blittable (pulled feature?)

C# 7.1

• Async Main – done, v10 (Oxygene, Swift and Java too)
• Default Expressions – done, v10
• Ref Assemblies
• Infer tuple names — done .2299
• Pattern-matching with generics

C# 7.0

Known planned changes for C# 7.0 as tracked on GitHub are:

• Address of Static
• Binary Literals — done, 9.0
• Digit Separators — done, 9.0
• Local Functions — done, v10 (Oxygene too)
• Patterns: Type switch
• Ref Returns
• Source Generation – not applicable
• Patterns: Throw Expr – done, v10 (Oxygene, Swift ands Java too)
• Tuple Syntax – done, v10
• out var Declarations — done, v10 (Oxygene too)
• ValueTask

Tentative C# 7.0 later changes:

• private protected Access Modifier done, v10
• Non-null Reference Types
• Better Overloading Rules
• Records
• With Exprs
• Pattern Matching