[rockfordlhotka]

Closes #4266

Summary

BusinessListBase, BusinessBindingListBase and BusinessDocumentBase skipped the deleted list during serialization only when the field was null. But IsDirty, IsBusy, CopyState and Deserialized() all read the lazily created DeletedList accessor. So in practice every list, even one fresh from Create, carried an empty deleted list in every MobileFormatter payload.

This change serializes the deleted list only when it contains items, which is how BusinessRules already handles _brokenRules. OnSetChildren resets the field to null when the payload has no deleted list, and the DeletedList accessor recreates it on demand. There is no public API change, and the accessor is still never null.

See the analysis comment on #4266 for why the null-vs-empty question is otherwise already settled.

Payload size (MobileFormatter, orders list with line-item child lists)

Graph	Lists	Before	After	Saved
1 order, 0 lines	2	1,958	1,646	15.9%
10 orders × 3 lines	11	18,116	17,417	3.9%
50 orders × 3 lines	51	84,676	82,257	2.9%
200 orders × 5 lines	201	479,976	471,107	1.8%

That works out to about 44 bytes per list, or 156 bytes for the first list of a type. Serialization time differences were within noise.

Tests

Added DeletedListSerializationTests, with three tests for each of the three list types:

• An empty deleted list (created by reading IsDirty) is not written to the payload.
• A non-empty deleted list round-trips, and the clone is dirty.
• A clone without a deleted list can still remove items, and ContainsDeleted and IsDirty behave correctly.

The full csla.test.sln suite (TestCategory!=SkipOnCIServer) passes on net10.0 and net11.0.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The focused changes preserve populated deleted lists and lazy initialization, with regression coverage and no blocking issues identified.

0 open findings

What changed in this PR

Reduces MobileFormatter payload sizes by omitting empty deleted lists across CSLA’s three editable collection types, addressing #4266.

Changes:

• Serialize deleted lists only when populated.
• Reset omitted deleted-list fields to null, preserving lazy initialization.
• Add nine regression tests and document the payload reduction.

File	Description
Source/​tests/​Csla.test/​Serialization/​DeletedListSerializationTests.cs	Tests omission, populated round-trips, and deletion after cloning.
Source/​Csla/​BusinessListBase.cs	Omits empty deleted lists and resets absent fields.
Source/​Csla/​BusinessDocumentBase.cs	Applies the same serialization behavior to documents.
Source/​Csla/​BusinessBindingListBase.cs	Applies the same serialization behavior to binding lists.
releasenotes.md	Documents the payload-size improvement.

🧠 Review effort: Balanced

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