Readme.md

sharpen.analyzer

Roslyn analyzers + code fixes to help modernize C# codebases.

Install

Two packages are published:

• Sharpen.Analyzer: diagnostics only (analyzers)
• Sharpen.Analyzer.FixProviders: diagnostics + IDE code fixes (depends on Sharpen.Analyzer)

Install one of them:

Option A: analyzers only

dotnet add package Sharpen.Analyzer

Option B: analyzers + code fixes (recommended)

dotnet add package Sharpen.Analyzer.FixProviders

Sharpen.Analyzer.FixProviders brings Sharpen.Analyzer automatically, so you don’t need to install both.

Use

Once the package is referenced, diagnostics are produced by Roslyn-based IDEs/editors and during dotnet build / dotnet test.

Bulk fixes (dotnet format)

To apply Sharpen analyzers as bulk fixes (outside the IDE), you can use dotnet format analyzers.

Example (run from the repo root):

dotnet format analyzers "Sharpen.Analyzer/Sharpen.Analyzer/Sharpen.Analyzer.Sample/Sharpen.Analyzer.Sample.csproj" --verbosity detailed --severity info

--severity info is important: many Sharpen rules are configured at info severity by default, and dotnet format analyzers will otherwise skip them.

Safety gate (code fix suppression)

Some code fixes are protected by a conservative “first-pass safety gate”. When a match is found but the transformation is deemed unsafe, the analyzer may still report the diagnostic, but the code fix will not be offered.

Enable / configure rules

Rules can be configured using .editorconfig (severity, enable/disable, etc.).

Example:

# .editorconfig

# SHARPEN004: Await Task.Delay instead of calling Thread.Sleep
# (example severity; adjust to your needs)
dotnet_diagnostic.SHARPEN004.severity = warning

Rules

See the Supported rules/features section below (source of truth).

Supported rules/features

Rules are grouped by the C# language version they target (when applicable).

C# 3

Rule ID	Title	Description	Code fix
SHARPEN002	Use var keyword in variable declaration with object creation	Prefer var when the type is obvious from the right-hand side object creation.	Yes

C# 5

Rule ID	Title	Description	Code fix
SHARPEN003	Use async equivalent	In an async caller, replace a synchronous invocation with an equivalent *Async method (and add await when needed).	Yes
SHARPEN004	Await Task.Delay instead of calling Thread.Sleep	Replace Thread.Sleep(...) with await Task.Delay(...) when the containing member can be made async.	Yes
SHARPEN005	Await Task instead of calling Task.Result	Replace .Result with await when safe.	Yes
SHARPEN006	Await Task instead of calling Task.Wait	Replace .Wait() with await when safe.	Yes
SHARPEN007	Await Task.WhenAny instead of calling Task.WaitAny	Replace Task.WaitAny(...) with await Task.WhenAny(...) when safe.	Yes
SHARPEN008	Await Task.WhenAll instead of calling Task.WaitAll	Replace Task.WaitAll(...) with await Task.WhenAll(...) when safe.	Yes
SHARPEN009	Consider awaiting equivalent asynchronous method and making the caller asynchronous	Suggest using an equivalent *Async method and making the caller async when possible.	Yes

C# 6

Rule ID	Title	Description	Code fix
SHARPEN010	Use expression-bodied member for get-only property	Convert a get-only property with a single return into an expression-bodied property.	Yes
SHARPEN011	Use expression-bodied member for get-only indexer	Convert a get-only indexer with a single return into an expression-bodied indexer.	Yes
SHARPEN012	Use nameof expression for parameter name	Replace string-literal parameter names in thrown argument exceptions with nameof(...).	Yes
SHARPEN013	Use nameof expression for dependency property name	Replace string-literal dependency property names in DependencyProperty.Register* calls with nameof(...).	Yes

C# 7

Rule ID	Title	Description	Code fix
SHARPEN014	Use expression-bodied member for get accessor in property	Convert a get { return ...; } accessor into get => ...; when possible.	Yes
SHARPEN015	Use expression-bodied member for constructor	Convert a simple constructor body into an expression-bodied constructor.	Yes
SHARPEN016	Use expression-bodied member for destructor	Convert a simple destructor body into an expression-bodied destructor.	Yes
SHARPEN017	Use expression-bodied member for local function	Convert a simple local function body into an expression-bodied local function.	Yes
SHARPEN018	Use out variables in method invocations	Use inline out var declarations in method calls.	Yes
SHARPEN019	Use out variables in object creations	Use inline out var declarations in object creation expressions.	Yes
SHARPEN020	Discard out variables in method invocations	Replace unused out variables with discards (out _).	Yes
SHARPEN021	Discard out variables in object creations	Replace unused out variables with discards (out _).	Yes

C# 7.1

Rule ID	Title	Description	Code fix
SHARPEN022	Use default expression in return statements	Prefer default over default(T) when the type can be inferred.	Yes
SHARPEN023	Use default expression in optional method parameters	Prefer default over default(T) in optional method parameters when the type can be inferred.	Yes
SHARPEN024	Use default expression in optional constructor parameters	Prefer default over default(T) in optional constructor parameters when the type can be inferred.	Yes

C# 8

Rule ID	Title	Description	Code fix
SHARPEN025	Replace using statement with using declaration	Convert using (...) { ... } to a C# 8 using declaration when safe.	Yes
SHARPEN026	Replace switch statement with switch expression	Convert a switch statement to a switch expression when safe.	Yes
SHARPEN027	Consider replacing switch statement with switch expression	Suggest converting a switch statement to a switch expression (conservative/heuristic).	Yes
SHARPEN028	Replace switch statement with switch expression	Convert a switch statement containing only assignments to a switch expression.	Yes
SHARPEN029	Consider replacing switch statement with switch expression	Suggest converting a switch statement containing only returns to a switch expression (conservative/heuristic).	Yes
SHARPEN030	Replace switch statement with switch expression	Convert a switch statement containing only returns to a switch expression.	Yes
SHARPEN031	Use ??= operator instead of assigning result of the ?? operator	Replace x = x ?? y with x ??= y when safe.	Yes
SHARPEN032	Consider using ??= operator instead of assigning result of the ?? operator	Suggest ??= when conversion might change semantics due to side effects.	Yes
SHARPEN033	Enable nullable context and declare identifier as nullable	Suggest enabling nullable context and marking identifiers as nullable where appropriate.	Yes
SHARPEN034	Use index from the end	Suggest using ^ (index-from-end) syntax where applicable.	No

C# 9

Rule ID	Title	Description	Code fix
SHARPEN035	Use init-only setter	Convert get; private set; auto-properties to init; when safe.	Yes
SHARPEN036	Use record type	Convert eligible sealed class data containers to record.	Yes
SHARPEN037	Use top-level statements	Convert a simple Program.Main entry point to top-level statements.	Yes
SHARPEN038	Use C# 9 pattern matching	Rewrite eligible boolean expressions using is not, relational patterns, and and patterns.	Yes
SHARPEN039	Use target-typed new	Replace new T(...) with new(...) when the target type is known and safe.	Yes

C# 10

Rule ID	Title	Description	Code fix
SHARPEN040	Use file-scoped namespace	Convert namespace X { ... } to namespace X; when safe.	Yes
SHARPEN041	Use global using directive	Suggest converting repeated using directives to global using (per-document fix; use “Fix all” to apply broadly).	Yes
SHARPEN042	Use record struct	Convert eligible struct value objects to record struct.	Yes
SHARPEN043	Use extended property pattern	Rewrite eligible expressions using C# 10 extended property patterns.	Yes
SHARPEN044	Use interpolated string	Replace string.Format(...) / concatenation with interpolated strings when safe.	Yes
SHARPEN045	Use const interpolated string	Replace constant concatenation / string.Format with const interpolated strings when safe.	Yes

C# 11

Rule ID	Title	Description	Code fix
SHARPEN046	Use raw string literal	Suggest raw string literals for multi-line or heavily-escaped strings.	Yes
SHARPEN047	Use required member	Add required to eligible properties.	Yes
SHARPEN048	Use generic math constraints	Suggest adding generic math constraints (e.g., where T : INumber<T>) when numeric operators are used on unconstrained type parameters.	No
SHARPEN049	Use list pattern	Suggest list patterns for common span/array length + indexing patterns.	Yes (limited)
SHARPEN050	Use UTF-8 string literal	Suggest replacing UTF-8 byte data with "..."u8 when type-compatible.	Yes

C# 12

Rule ID	Title	Description	Code fix
SHARPEN051	Use primary constructor	Convert assignment-only constructors to primary constructors when safe.	Yes (experimental)
SHARPEN052	Use collection expression	Convert eligible array/collection initializers to C# 12 collection expressions ([...]).	Yes
SHARPEN053	Use default lambda parameters	Use default values in explicitly-typed lambda parameter lists when applicable.	Yes
SHARPEN054	Use InlineArray	Convert fixed-size buffer-like structs to [InlineArray(N)] when safe.	Yes

C# 13

Rule ID	Title	Description	Code fix
SHARPEN058	Prefer params collections	Suggest migrating non-public params T[] to collection-based params when safe.	Yes
SHARPEN059	Use from-end index in object initializers	Suggest using ^ indices in object/collection initializers when provably equivalent.	Yes
SHARPEN060	Use \e escape sequence	Suggest replacing \u001b / \x1b with \e when unambiguous.	Yes
SHARPEN061	Use System.Threading.Lock	Suggest migrating dedicated private lock objects to System.Threading.Lock when available and safe.	Yes
SHARPEN062	Partial properties/indexers refactoring	Suggest/refactor eligible members to C# 13 partial properties/indexers when safe.	No (refactoring)
SHARPEN063	Suggest allows ref struct constraint	Guidance-only: suggest allows ref struct for eligible generic APIs.	No
SHARPEN064	Suggest OverloadResolutionPriorityAttribute	Guidance-only: suggest OverloadResolutionPriorityAttribute for eligible overload sets.	No

Development

Open Sharpen.Analyzer/Sharpen.Analyzer.sln and run the test project (Sharpen.Analyzer.Tests).

Contributing

See todo.md for the current backlog and notes.