A code rule can rely on an NDepend.CodeModel.ICompareContext object to query the diff between 2 snapshots of a code base, the newer snapshot and the baseline snapshot. For example rules to detect API breaking changes fall in this category. Such rule can match code elements in the baseline code base snapshot.

However the issue code element returned by NDepend.CodeModel.ICodeElement necessarily belongs to the newer code base snapshot. In such situation this property returns the matched code element declared in the baseline code base, and the code element returned by CodeElement is the most inner parent code element of CodeElementInBaseline, that has an equivalent in the newer code base snapshot.
If not in the situation, which means that the matched code element is declared in the newer code base snapshot, this property returns null.

Reference

IIssue Interface
IIssue Members