Keep the key comparer when deep cloning a dictionary - #79
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The IDictionary and IReadOnlyDictionary overloads always built a Dictionary with the default comparer. A cloned case-insensitive dictionary stopped finding keys, and a SortedDictionary came back unordered. They now build a dictionary of the same kind, with the same comparer, when the runtime type is a Dictionary or a SortedDictionary. New concrete Dictionary and SortedDictionary overloads keep the comparer too. Because both types implement IDictionary and IReadOnlyDictionary, these overloads also let dictionary.DeepClone() compile without a cast (CS0121). Fixes #77 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NvZoJBSka1emZMaEXy4Cfj
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This was referenced Sep 26, 2026
This was referenced Sep 28, 2026
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Fixes #77
What was wrong
The
IDictionaryandIReadOnlyDictionaryoverloads ofDeepClone()usedToDictionary, which always builds aDictionarywith the default comparer:OrdinalIgnoreCasedictionary no longer found"key".SortedDictionarycame back as an unorderedDictionary.Separately,
dict.DeepClone()on aDictionary<,>didn't compile (CS0121), because it matches both interface overloads equally well.Change
CloneDictionaryhelper.SortedDictionary<,>, it builds aSortedDictionarywith the same comparer.Dictionary<,>, it builds aDictionarywith the same comparer.Dictionary, as before.Dictionary<TKey,TValue> DeepClone(this Dictionary<TKey,TValue>)andSortedDictionary<TKey,TValue> DeepClone(this SortedDictionary<TKey,TValue>).[minor]because it adds public API. Existing call sites that cast to an interface behave the same apart from keeping the comparer.Tests
New tests in
SpecializedCollectionTests:Dictionary_DeepCloneAsIDictionary_KeepsComparerandDictionary_DeepCloneAsIReadOnlyDictionary_KeepsComparer: a case-insensitive lookup still works after cloning.SortedDictionary_DeepCloneAsIDictionary_KeepsTypeAndComparer: the clone is still sorted, with a custom descending comparer.Dictionary_DeepClone_WithoutCast_KeepsComparerAndClonesValues,SortedDictionary_DeepClone_WithoutCast_KeepsComparerandDictionary_DeepClone_Null_ShouldThrow: the concrete overloads.Verification
main, the three interface tests fail (ContainsKey("key")is false, and the clone's type isDictionary).main, the three concrete-call tests don't compile, with CS0121 between the two interface overloads.netstandard2.0included, has no warnings.🤖 Generated with Claude Code
https://claude.ai/code/session_01NvZoJBSka1emZMaEXy4Cfj
Generated by Claude Code