Hashtable and DictionaryEntry

HashTable Class of System.Collections namespace represents a collection of key/value pairs that are organized based on the hash code of the key.

using System.Collections;

Hashtable ht = new Hashtable();
private void Form1_Load(object sender, EventArgs e)
{
	ht.Add("Am", "Ambily");
	ht.Add("Di", "Divya");
	foreach (DictionaryEntry de in ht)
	{
		listBox1.Items.Add(de.Key);
		listBox2.Items.Add(de.Value);
	}
}

private void button1_Click(object sender, EventArgs e)
{
	ht.Add(textBox1.Text, textBox2.Text);
	ShowHashTable();
}

private void ShowHashTable()
{
	listBox1.Items.Clear();
	listBox2.Items.Clear();
	foreach (DictionaryEntry de in ht)
	{
		listBox1.Items.Add(de.Key);
		listBox2.Items.Add(de.Value);
	}
}

VB .Net

Dim ht As New Hashtable
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
	ht.Add("Am", "Ambily")
	ht.Add("Di", "Divya")
	ShowHT()
End Sub
Private Sub ShowHT()
	ListBox1.Items.Clear()
	ListBox2.Items.Clear()
	For Each de As DictionaryEntry In ht
		ListBox1.Items.Add(de.Key)
		ListBox2.Items.Add(de.Value)
	Next
End Sub
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
	ht.Add(txtKey.Text, txtValue.Text)
	ShowHT()
End Sub

Related Blog ReadOnlyCollectionBase Class Generics and Collection Initializer in .Net

ReadOnlyCollectionBase Class

Provides the abstract base class for a strongly typed non-generic read-only collection.This class makes the underlying collection available through the InnerList property.
Since ReadOnlyCollectionBase implements IEnumerable Interface you can iterate through the collection.

//class
using System.Collections;
class ShalvinBlogs : ReadOnlyCollectionBase
{
public void Add(String value)
{
InnerList.Add(value);
}
public string this[int index]
{
get
{
return (string)InnerList[index];
}
}
}

//Forms
ShalvinBlogs sb = new ShalvinBlogs();

private void Form1_Load(object sender, EventArgs e)
{
sb.Add("Shalvinpd.blogspot.com");
sb.Add("DotNetShalvin.blogspot.com");
foreach (string str in sb)
listBox1.Items.Add(str);
}
private void button1_Click(object sender, EventArgs e)
{
textBox1.Text = sb[0];
}

Related Blogs
Generics and Collection Initializer in .Net
Hashtable and DictionaryEntry