C# hashtable
The Hashtable class represents a series of key/value pairs organized by key-based hash code. It uses keys to access elements in the collection.
When you use keys to access elements, a hash table is used, and you can identify a useful key value. Each item in the hash table has a key/value pair. Key is used to access items in the collection.
Methods and properties of the Hashtable class
The following table lists some common properties of Hashtable class:
Attribute |
Description |
|---|---|
Count |
Gets the number of key-value pairs contained in Hashtable. |
IsFixedSize |
Gets a value indicating whether the Hashtable has a fixed size. |
IsReadOnly |
Gets a value indicating whether the Hashtable is read-only. |
Item |
Gets or sets the value associated with the specified key. |
Keys |
Gets an ICollection containing the keys in the Hashtable. |
Values |
Gets an ICollection that contains the value in the Hashtable. |
The following table lists some common methods of Hashtable:
Serial number |
Method name & description |
|---|---|
1 |
Public virtual void Add (object key, object value); adds an element with thespecified key and value to Hashtable. |
2 |
Public virtual void Clear (); removes all elements from the Hashtable. |
3 |
Public virtual bool ContainsKey (object key); determines whether the Hashtable contains the specified key. |
4 |
Public virtual bool ContainsValue (object value); determines whether the Hashtable contains the specified value. |
5 |
Public virtual void Remove (object key); removes the element with the specified key from the Hashtable. |
Example
The following example demonstrates the concept of a Hashtable:
Example
using System;
using System.Collections;
namespace CollectionsApplication
{
class Program
{
static void Main(string[] args)
{
Hashtable ht = new Hashtable();
ht.Add("001", "Zara Ali");
ht.Add("002", "Abida Rehman");
ht.Add("003", "Joe Holzner");
ht.Add("004", "Mausam Benazir Nur");
ht.Add("005", "M. Amlan");
ht.Add("006", "M. Arif");
ht.Add("007", "Ritesh Saikia");
if (ht.ContainsValue("Nuha Ali"))
{
Console.WriteLine("This student name is already in the
list");
}
else
{
ht.Add("008", "Nuha Ali");
}
// Get a collection of keys
ICollection key = ht.Keys;
foreach (string k in key)
{
Console.WriteLine(k + ": " + ht[k]);
}
Console.ReadKey();
}
}
}
When the above code is compiled and executed, it produces the following results:
007: Ritesh Saikia
004: Mausam Benazir Nur
005: M. Amlan
008: Nuha Ali
002: Abida Rehman
003: Joe Holzner
001: Zara Ali
006: M. Arif