Difference Between Dictionary And Hashtable In C#

Dictionary and Hashtable in C# store key-value pairs, but differ in performance, memory consumption, and thread safety. Hashtable is older and less efficient, while Dictionary offers better performance and type safety.

Dictionary and Hashtable in C# are used to hold data as a collection of key-value pair. This blog talks about some differences between a dictionary and a hashtable.

The following code snippet creates a Dictionary in C#.

Dictionary<string, string> EmployeeList = new Dictionary<string, string>();

// Adding items to the dictionary
EmployeeList.Add("Mahesh Chand", "Programmer");
EmployeeList.Add("Praveen Kumar", "Project Manager");
EmployeeList.Add("Raj Kumar", "Architect");
EmployeeList.Add("Nipun Tomar", "Asst. Project Manager");
EmployeeList.Add("Dinesh Beniwal", "Manager");

The following code snippet creates a HashTable in C#.

Hashtable HT = new Hashtable();
HT.Add(1, "s");
HT.Add(3, "n");
HT.Add(4, "j");
HT.Add(2, "a");
HT.Add(5, "u");

At some point, you will need to make a decision as to which of these two objects to use. Here are some of the key differences between the two.

Dictionary

1. The dictionary is generic type Dictionary<TKey, TValue>
2. Dictionary class is a strong type < TKey, TValue > Hence, you must specify the data types for key and value.
3. There is no need for boxing/unboxing.
4. When you try to access the nonexisting key dictionary, it gives a runtime error.
5. The dictionary maintains an order of the stored values.
6. There is no need for boxing/unboxing, so it is faster than Hashtable.

Hashtable

1. Hashtable is a non-generic type.
2. Hashtable is a weakly typed data structure, so you can add keys and values of any object type.
3. Values need to have boxing/unboxing.
4. When you try to access non existing key Hashtable, it gives null values.
5. Hashtable never maintains an order of the stored values.
6. Hashtable needs boxing/unboxing, so it is slower than Dictionary.

Next: Using Dictionary in C#and Understanding C# HashTable