ASP.NET HashTable
A Hashtable is a data structure that embodies a sophisticated collection of key/value pairs, skillfully associating keys with their corresponding values. It serves as a mechanism for mapping unique keys to specific values. In this structure, keys hold major importance and can be assigned any non-null object, providing utmost flexibility. Conversely, values within the Hashtable must possess the ability to store any object, ensuring versatility in accommodating various data types.
To access the stored information, one can elegantly retrieve items from the Hashtable by referencing their respective keys. This retrieval process ensures a seamless and efficient means of accessing the desired values within the collection. It is worth noting that both the keys and the values themselves are treated as Objects, allowing for a wide range of data to be employed and manipulated within this framework.
Add a pair of values in a HashTable
VB.Net
Dim ht As New Hashtable
ht.Add("1", "Sunday")
ht.Add("2", "Monday")
C#
Hashtable ht = new Hashtable();
ht.Add("1", "Sunday");
ht.Add("2", "Monday");
Check if a specified key exist or not
VB.Net
ht.Contains("1")
C#
ht.Contains("1");
The above code return true if item exist else false.
Remove the specified Key and corresponding Value
HashTable.Remove(Key) VB.Net
ht.Remove("1")
C#
ht.Remove("1");
Display all key value pairs
VB.Net
For Each item In ht
Label1.Text = item.Key & " -- " & item.Value
Next
C#
foreach (DictionaryEntry item in ht)
{
Label1.Text = item.Key + " - " + item.Value;
}
The following ASP.NET program add seven days in a week to a HashTable and bind it to a ListBox control.
Default.aspx
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
<br />
<asp:ListBox ID="ListBox1" runat="server"></asp:ListBox><br />
</div>
</form>
</body>
</html>
Full Source | C#
using System;
using System.Collections;
public partial class _Default : System.Web.UI.Page
{
protected void Button1_Click(object sender, EventArgs e)
{
Hashtable ht = new Hashtable();
ht.Add("1", "Sunday");
ht.Add("2", "Monday");
ht.Add("3", "Tuesday");
ht.Add("4", "Wednesday");
ht.Add("5", "Thursday");
ht.Add("6", "Friday");
ht.Add("7", "Saturday");
ListBox1.DataSource = ht;
ListBox1.DataValueField = "Key";
ListBox1.DataTextField = "Value";
ListBox1.DataBind();
}
}
Full Source | VB.NET
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim ht As New Hashtable
ht.Add("1", "Sunday")
ht.Add("2", "Monday")
ht.Add("3", "Tuesday")
ht.Add("4", "Wednesday")
ht.Add("5", "Thursday")
ht.Add("6", "Friday")
ht.Add("7", "Saturday")
ListBox1.DataSource = ht
ListBox1.DataValueField = "Key"
ListBox1.DataTextField = "Value"
ListBox1.DataBind()
End Sub
End Class
Conclusion
A Hashtable is a remarkable tool that facilitates the organization and management of key/value pairs, enabling the retrieval of stored items through key-based referencing. It empowers developers to handle complex data structures with ease, as it accommodates diverse objects as keys and values, thereby enhancing its overall flexibility and applicability.