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:

Yourdefault branch, with results shown on the repository's "Standard findings" dashboard
Pull requests, with findings shown as comments made bygithub-code-quality[bot]

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 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 assignment to local variable	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 is constant	Reliability	Warning
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

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C# CodeQL queries for Code Quality