Hashtable Dictionary Hashtable included in System.Collections namespace Dictionary included in System.Collections.Generic namespace It is weakly structured data type in key values pair we can take any object type In this strong in a data type that you must have to specify the data type of the key value  pair Returns null as a result if key which does not exist Throws exception if we try to find with a key that not exists It is generic type It is non-generic type It is faster since we don’t need to do boxing and unboxing in this It is slower than hashtable and it involves an additional step of boxing and unboxing