C#: Add change note.

aschackmull · aschackmull · commit afc98cacbedf · 2025-09-17T12:49:25.000+02:00
diff --git a/csharp/ql/src/change-notes/2025-09-17-nullguard-pattern.md b/csharp/ql/src/change-notes/2025-09-17-nullguard-pattern.md
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+---
+category: minorAnalysis
+---
+* The modeling of null guards based on complex pattern expressions has been improved, which in turn improves the query `cs/dereferenced-value-may-be-null` by removing false positives.

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 +---
 +category: minorAnalysis
 +---
 +* The modeling of null guards based on complex pattern expressions has been improved, which in turn improves the query `cs/dereferenced-value-may-be-null` by removing false positives.