Why is Dictionary preferred over hashtable?

In Hashtable type casting will be required so performance wise Dictionary is preferred.

Below are some differences between them : 

Dictionary:

• It returns error if we try to find a key which does not exist.
• It is faster than a Hashtable because there is no boxing and unboxing.
• Only public static members are thread safe.
• Dictionary is a generic type which means we can use it with any data type.

Hashtable:

• It returns null if we try to find a key which does not exist.
• It is slower than dictionary because it requires boxing and unboxing.
• All the members in a Hashtable are thread safe,
• Hashtable is not a generic type,