Difference between Hashtable and Dictionary

Question

Ashutosh Kumar Verma · Answer

Dictionary vs Hashtable in C#
In C#, Hashtable and Dictionary are used to store key-value pairs, but they have some differences in terms of functionality, implementation and features,
and 
Dictionaryand 
There are several points in Dictionary that make it different from Hashtable which are as follows,
Namespace- Dictionary is present in the System.Collections.Generic namespace.
Type Safety- The Dictionary is type-safe, you must specify the
data type for both the keys and the values
​​when you declare it.
Performance- Dictionary usually provides better performance than
Hashtable since it is a generic collection and avoids boxing/unboxing overhead
Null Keys- the Dictionary does not allow the 
null key but allows null values.
Enumeration- Enumerating over a dictionary with 
foreach is more efficient than enumerating over a hashtable.
Enumeration Order- Dictionary does not guarantee the order of the elements while
Hashtable also does not preserve the order of the elements.
Obsolete- The dictionary is a newer and preferred alternative to
key-value pairs in most cases.
Example-and 
using System;
using System.Collections.Generic;
class Program
{
   static void Main()
   {
       // Creating a Dictionary
       Dictionaryandlt;string, string> dictionary = new Dictionaryandlt;string, string>();
       // Adding key-value pairs to the Dictionary
       dictionary.Add("1", "One");
       dictionary.Add("2", "Two");
       dictionary.Add("3", "Three");
       // Accessing elements in the Dictionary
       Console.WriteLine("Value at key '1': " + dictionary["1"]);
       Console.WriteLine("Value at key '2': " + dictionary["2"]);
       Console.WriteLine("Value at key '3': " + dictionary["3"]);
       // Iterate over dictionary
       Console.WriteLine("
 Iterate over dictionary:");
       foreach (KeyValuePairandlt;string, string> pair in dictionary)
       {
           Console.WriteLine("Key: " + pair.Key + ", Value: " + pair.Value);
       }
       Console.ReadLine();
   }
}
Output-
Value at key '1': One
Value at key '2': Two
Value at key '3': Three
Iterate over dictionary:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
and 
Hashtable
There are also some points in Hashtable that differ from Dictionary which are as follow,
Namespace- Dictionary is present in the System.Collections namespace.
Type Safety- The Hashtable is not type-safe, because it allows any
datatype for both key and value.
Performance- Hashtable uses a simple hash code
algorithm that's why its performance is not as good as Dictionary
Null Keys- The Hashtable allows both the 
null key and null value
Enumeration- Hashtable needs boxing/unboxing, which can degrade performance during calculation.
Enumeration Order- The Hashtable doesn't preserve the order of the elements.
Obsolete- The Hashtable is a part of an older non-generic collection framework in C#
and 
Example-and 
using System;
using System.Collections;
class Program
{
   static void Main()
   {
       // Creating a Hashtable
       Hashtable hashtable = new Hashtable();
       // Adding key-value pairs to the Hashtable
       hashtable.Add("1", "One");
       hashtable.Add("2", "Two");
       hashtable.Add("3", "Three");
       // Accessing elements in the Hashtable
       Console.WriteLine("Value at key '1': " + hashtable["1"]);
       Console.WriteLine("Value at key '2': " + hashtable["2"]);
       Console.WriteLine("Value at key '3': " + hashtable["3"]);
       // Iterating through the Hashtable
       Console.WriteLine("
Iterating through the Hashtable:");
       foreach (DictionaryEntry entry in hashtable)
       {
           Console.WriteLine("Key: " + entry.Key + ", Value: " + entry.Value);
       }
   }
}
Output-
Value at key '1': One
Value at key '2': Two
Value at key '3': Three
Iterating over the Hashtable:
Key: 2, Value: Two
Key: 3, Value: Three
Key: 1, Value: One
and 
Also, Read: Pascal Triangle

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Difference between Hashtable and Dictionary

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Dictionary vs Hashtable in C#

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