VB.NET NameValueCollection

The NameValueCollcetion class is similar to HashTable that stores a collection of different data items in keys and associated values in string type. The class is provided by the System.Collection Namespace. The NameValueCollection can store more than one value under a single key separated by a comma.

Properties of the NameValueCollection Class

The following are the commonly used property of NameValueCollection:

Property name	Description
AllKeys	It is used to get all the keys in the NameValueCollection
Count	It is used to count the number of key/value pair elements available in the NameValueCollection.
IsReadOnly	It is used to get or set a value that determines whether the NameValueCollection is read-only.
Item	It is used to get or set a value associated with the specified key in the NameValueCollection.
Keys	It is used to get all the keys that have instances in the NameValueCollection.
Values	It is used to obtain a collection of values in a NameValueCollection.

NameValueCollection Methods

The following are the commonly used methods of NameValueCollection.

Methods Name	Description
Add	It is used to add an element with the specified name and value into the NameValueCollection. Syntax: NameValueCollection.Add(key, 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 entries from the NameValueCollection.
Get(String)	A Get() function is used to obtain a particular value of the specified index from the NameValueCollection that are comma-separated list. Syntax: NameValueCollection.Get(Key)
HasKeys()	A HasKeys() function is used to get a value that represents whether the NameValueCollection has keys that are not null. Syntax: NameValueCollection.HasKey()
GetValues(String)	It is used to get all the values of a specified key or index from the NameValueCollection. Syntax: GetValues (ByVal str As String) As String()
Set()	In NameValueCollection, a Set() function is used to set or overwrite the existing value of the key. Syntax: Set(String, String)
Equals()	The Equals() function is used to validate whether the specified object matches the current object.

Let us create a program to understand how we can add new elements to a NameVal array.

NameVal.vb

Imports System.Collections.Specialized
Module NameVal
    Sub Main()
        'Defining an array NVCol As NameValueCollection
        Dim NVCol As NameValueCollection = New NameValueCollection()
        Dim key As String
        'Use of Add() function
        NVCol.Add("flower", "Rose")
        NVCol.Add("flower", "Lotus")
        NVCol.Add("flower", "Sunflower")
        NVCol.Add("planet", "Earth")
        NVCol.Add("planet", "Mars")
        NVCol.Add("planet", "Mercury")
        NVCol.Add("planet", "Jupiter")

        For Each key In NVCol
            Console.WriteLine("Key Name: {0} ", key)
            Console.WriteLine("Elements are: {0} ", NVCol.Get(key))
        Next
        Console.WriteLine()

        'Display the First Key
        Console.WriteLine("Name of first Key is: {0}", NVCol.GetKey(1))

        'Display the First value of Key using the GetValues(key)
        Console.WriteLine("Value of first Key is: {0}", NVCol.GetValues(0))

        Console.WriteLine(" Total keys in NameValueCollection {0}", NVCol.Count)
        Console.WriteLine()

        'Use of Remove() function
        Console.WriteLine(" Remove key 'flower' from NameValueCollection ")
        NVCol.Remove("flower")
        For Each key In NVCol
            Console.WriteLine("Current Key Name: {0} ", key)
            Console.WriteLine("Current Key Elements are: {0} ", NVCol.Get(key))
        Next
        Console.WriteLine()

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

Output: