Use Dictionary with StringComparer to avoid string allocations in System.Data.Common #120603
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October 10, 2025 16:40
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| columnName = columnName.ToLowerInvariant(); |
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Also before the hash.TryAdd about 20 lines lower?
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Issue
System.Data.Common.ADPinternal helper class hasBuildSchemaTableInfoTableNamesmethod that callsToLowerInvarianton astringin a loop only to perform a dictionary lookup.Suggested fix
Using
Dictionary<K, V>withStringComparer.InvariantCultureIgnoreCasecan avoid multiplestringallocations in that method.How issue was found
I came up with an idea of an analyzer that would look for
Dictionary<string, TValue>lookups and find cases when a string allocation is made only to perform a lookup. In such a case an analyzer could recommend usingDictionary<K, V>.GetAlternateLookup<ReadOnlySpan<char>>to avoid an allocation. I prototyped such an analyzer and ran it as a standalone analysis tool against projects that are part ofsrc/libraries/sfx.slnxsolution. This is how I found this code. And in this particular case, I actually realized it should be even easier to fix by usingStringComparer. This could probably be a second rule in the same analyzer.Analyzer proposal
[I'll provide a link to the proposal shortly]