No, the documentation for Dictionary doesn’t make this guarantee, it’s explicit that readers are only allowed as long as the collection isn’t modified: https://

No, the documentation for Dictionary doesn’t make this guarantee, it’s explicit that readers are only allowed as long as the collection isn’t modified: https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2?view=net-7.0#thread-safety https://learn.microsoft.com/en-us/dotnet/api/system.collecti... Maybe that guarantee was too strong and prevented a more efficient implementation.