What is the Difference Between Dictionary and Hashtable?

The main difference between a Dictionary and a Hashtable lies in their data types, performance, and thread safety. Here are the key differences between the two:

1. Data Type:

• Hashtable is a non-generic collection, which means it can store key-value pairs of any data types.
• Dictionary is a generic collection, which means it can only store key-value pairs of specific data types.

1. Performance:

• Data retrieval in a Hashtable is slower due to boxing and unboxing.
• Data retrieval in a Dictionary is faster because it is type-safe, eliminating the need for boxing and unboxing.

1. Thread Safety:

• Hashtable is fully thread-safe.
• Only public static members of Dictionary are thread-safe.

1. Key Existence Checking:

• If you try to access a key that doesn't exist in a Hashtable, it returns null.
• If you try to access a key that doesn't exist in a Dictionary, it throws an exception.

1. Order:

• A Hashtable does not maintain the order of the inserted key-value data.
• A Dictionary maintains the insertion order of stored values.

In summary, a Dictionary is a faster, type-safe, and ordered collection compared to a Hashtable. It is generally recommended to use a Dictionary over a Hashtable due to its performance and type safety benefits.

Comparative Table: Dictionary vs Hashtable

Here is a table comparing the differences between Dictionary and Hashtable in C#:

In summary, Hashtable is a non-generic collection that stores key/value pairs of any data types, and it is included in the System.Collections namespace. Meanwhile, Dictionary is a generic collection that stores key/value pairs of specific data types and is included in the System.Collections.Generic namespace. The Dictionary class is preferred over Hashtable due to its type safety, improved performance, and better integration with the C# language.