VB.NET HashTable

A HashTable is used to store the collection of different types of data in key-value pairs. These table data are organized based on the hash key. A HashTable is provided by the System.Collection namespace. A Key is used to identify and access each element of the HashTable because each item in the HashTable has a Key/value pair.

HashTable Properties

The following table describes the properties of the HashTable

Property Name	Description
IsSynchronized	It is used to obtain a value that determines whether the HashTable is synchronized.
IsFixedSize	It is used to obtain a value that determines whether a HashTable has a fixed size.
Count	It is used to count the number of key/value pair elements available in the HashTable.
IsReadOnly	It is used to obtain a value that determines whether the HashTable is read-only.
Item	It is used to get or set a value associated with the specified key.
Keys	It is used to obtain a collection of keys in a HashTable.
Values	It is used to obtain a collection of values in a HashTable.

HashTable Methods

The Following are the commonly used method of the HashTable in the VB.NET.

Methods Name	Description
Add	It is used to add an element with the specified key and value into the HashTable. Syntax: HashTable.Add(key, value)
ContainsKey	It is used to check whether the specified key exists or not in HashTable. Syntax: HashTable.ContainsKey(key)
ContainsValue	It is used to check whether the specified value of the key is existing or not in HashTable. Syntax: HashTable.ContainsValue(value)
Remove	The Remove function is used to remove the specified key with the corresponding value. Syntax: HashTable.Remove(Key)
Clear	It is used to remove all the elements from the HashTable.
GetHash	A GetHash is used to get the hash code of the specified key in HashTable/

Let's create a program to understand the concept of HashTable in the VB.NET programming language.

Array_Hash.vb

Imports System.Collections
Module Array_Hash
    Sub Main()
        Dim hashTab As Hashtable = New Hashtable()
        Dim j As DictionaryEntry
        'Use of Add() function
        hashTab.Add("str", "VB.NET")
        hashTab.Add("05", "Peter")
        hashTab.Add("06", "Hamilton")
        hashTab.Add("07", "Universe")
        hashTab.Add("08", "Welcome")
        hashTab.Add("09", 90)
        hashTab.Add("site", "JavaTpoint")
        hashTab.Add("planet", "Earth")

        For Each j In hashTab
            Console.WriteLine(" Key = {0}, Value = {1}", j.Key, j.Value)
        Next j
        Console.WriteLine()

        ' Use of ContainsValue() function
        If hashTab.ContainsValue("Earth") Then
            Console.WriteLine(" Value 'Earth' is exist")
        Else
            Console.WriteLine(" Doesn't exist")
        End If
        Console.WriteLine(" Total keys in HashTable {0}", hashTab.Count)

        'Display a Single item.
        Console.WriteLine("Display a Single item is '{0}' from HashTab", hashTab("07"))

        'Use of ContainsKey() function
        'Console.WriteLine(" Is the key '05' exist : {0) ", hashTab("05"))

        'Use of Remove() function
        Console.WriteLine(" Remove key 07 from HashTab ")
        hashTab.Remove("07")
        For Each j In hashTab
            Console.WriteLine(" Key = {0}, Value = {1}", j.Key, j.Value)
        Next j

        Console.WriteLine(" Press any key to exit")
        Console.ReadKey()
    End Sub
End Module

Output: