C# CodeQL queries for Code Quality

Explore the queries that CodeQL uses to analyze code quality for code written in C#.

Code Quality uses the following CodeQL queries to analyze C# code and detect code quality issues on:

Copilot Autofix suggestions are provided for findings where possible.

Query name Category Severity
Block code with a single Response.Write() Maintainability Recommendation
Call to obsolete method Maintainability Warning
Class has same name as super class Maintainability Recommendation
Class implements ICloneable Maintainability Recommendation
Constant condition Maintainability Warning
Container contents are never accessed Maintainability Error
Field masks field in super class Maintainability Warning
Futile conditional Maintainability Warning
Local scope variable shadows member Maintainability Recommendation
Missed 'readonly' opportunity Maintainability Recommendation
Missed 'using' opportunity Maintainability Recommendation
Missed opportunity to use All Maintainability Recommendation
Missed opportunity to use Cast Maintainability Recommendation
Missed opportunity to use FirstOrDefault Maintainability Recommendation
Missed opportunity to use OfType Maintainability Recommendation
Missed opportunity to use Select Maintainability Recommendation
Missed opportunity to use Where Maintainability Recommendation
Missed ternary opportunity Maintainability Recommendation
Nested 'if' statements can be combined Maintainability Recommendation
Redundant Select Maintainability Warning
Redundant ToString() call Maintainability Recommendation
Static field written by instance method Maintainability Recommendation
Unnecessarily complex Boolean expression Maintainability Recommendation
Unused label Maintainability Warning
Useless call to GetHashCode() Maintainability Recommendation
A lock is held during a wait Reliability Warning
Call to 'System.IO.Path.Combine' may silently drop its earlier arguments Reliability Recommendation
Call to GC.Collect() Reliability Warning
Call to ReferenceEquals(...) on value type expressions Reliability Error
Calls to unmanaged code Reliability Recommendation
Cast of 'this' to a type parameter Reliability Recommendation
Character passed to StringBuilder constructor Reliability Error
Comparison of identical values Reliability Warning
Container contents are never initialized Reliability Error
Container size compared to zero Reliability Warning
Dereferenced variable is always null Reliability Error
Dereferenced variable may be null Reliability Warning
Dubious downcast of 'this' Reliability Warning
Dubious type test of 'this' Reliability Warning
Empty branch of conditional, or empty loop body Reliability Warning
Empty lock statement Reliability Warning
Equality check on floating point values Reliability Warning
Equals on collections Reliability Recommendation
Equals on incomparable types Reliability Error
Exposing internal representation Reliability Recommendation
Futile synchronization on field Reliability Error
Generic catch clause Reliability Recommendation
Hashed value without GetHashCode definition Reliability Warning
Impossible array cast Reliability Error
Inconsistent lock sequence Reliability Error
Inefficient use of ContainsKey Reliability Recommendation
Invalid string formatting Reliability Error
Locking the 'this' object in a lock statement Reliability Warning
Missing Dispose call on local IDisposable Reliability Warning
Nested loops with same variable Reliability Warning
Null argument to Equals(object) Reliability Warning
Off-by-one comparison against container length Reliability Error
Poor error handling: catch of NullReferenceException Reliability Warning
Poor error handling: empty catch block Reliability Recommendation
Possible loss of precision Reliability Error
Potentially dangerous use of non-short-circuit logic Reliability Error
Property value is not used when setting a property Reliability Warning
Recursive call to Equals(object) Reliability Error
Rethrowing exception variable Reliability Warning
Self-assignment Reliability Error
String concatenation in loop Reliability Recommendation
StringBuilder creation in loop Reliability Recommendation
Unchecked cast in Equals method Reliability Warning
Unmanaged code Reliability Recommendation
Use of default ToString() Reliability Warning