codeql/change-notes/1.23/analysis-csharp.md

Improvements to C# analysis

The following changes in version 1.23 affect C# analysis in all applications.

New queries

New queries

Query	Tags	Purpose
Unsafe year argument for 'DateTime' constructor (cs/unsafe-year-construction)	reliability, date-time	Finds incorrect manipulation of DateTime values, which could lead to invalid dates.
Mishandling the Japanese era start date (cs/mishandling-japanese-era)	reliability, date-time	Finds hard-coded Japanese era start dates that could be invalid.

Changes to existing queries

Query	Expected impact	Change

Removal of old queries

Changes to code extraction

• nameof expressions are now extracted correctly when the name is a namespace.

Changes to QL libraries

• The new class NamespaceAccess models accesses to namespaces, for example in nameof expressions.
• The data-flow library now makes it easier to specify barriers/sanitizers arising from guards by overriding the predicate isBarrierGuard/isSanitizerGuard on data-flow and taint-tracking configurations respectively.
• The data-flow library has been extended with a new feature to aid debugging. Instead of specifying isSink(Node n) { any() } on a configuration to explore the possible flow from a source, it is recommended to use the new Configuration::hasPartialFlow predicate, as this gives a more complete picture of the partial flow paths from a given source. The feature is disabled by default and can be enabled for individual configurations by overriding int explorationLimit().
• foreach statements where the body is guaranteed to be executed at least once, such as foreach (var x in new string[]{ "a", "b", "c" }) { ... }, are now recognized by all analyses based on the control flow graph (such as SSA, data flow and taint tracking).

Changes to autobuilder