What is the difference between a HashTable and Dictionary in C#?

Hashtable is a non-generic collection that stores keys and values as objects. This leads to boxing and unboxing for value types and requires explicit casting when retrieving values — which can hurt performance and cause runtime errors.

Dictionary<TKey, TValue> is the generic, type-safe replacement introduced in .NET 2. It avoids boxing/unboxing, improves performance, and gives compile-time safety. It also integrates better with LINQ and modern .NET features.

I always prefer Dictionary in new codebases. I’ve only worked with Hashtable in maintaining legacy systems.

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