ASP.NET List
How to use Asp.Net List
The Collection classes are a set of classes designed specifically for grouping together objects and performing tasks on them. The basic functionality of collection classes are Adding elements to the Collection, Removing elements from the collection, Obtaining number of elements in the collection atc. List class is a Collection member and defined in the System.Collections.Generic namespace.
The C# List < T > class represents a strongly typed list of objects that can be accessed by index. Elements in the List can be accessed using an integer index. Indexes in this collection are zero-based.
|BLBS^ |List < T > |BLBE^ |
The parameter T is the type of elements in the list.
Add items in List collection ?
Add Integer values in the List collection
C#
List < int > intList = new List< int > ();
intList.Add(20);
intList.Add(30);
intList.Add(50);
intList.Add(70);
VB.Net
Dim intList As New List(Of Integer)()
intList.Add(20)
intList.Add(30)
intList.Add(50)
intList.Add(70)
Add String values in the List
C#
months.Add("January");
months.Add("Frebruary");
months.Add("March");
months.Add("April");
months.Add("May");
months.Add("June");
VB.Net
months.Add("January")
months.Add("Frebruary")
months.Add("March")
months.Add("April")
months.Add("May")
months.Add("June")
Obtaining the number of elements in a List ?
You can use "count" property to know the number of items in the List collection
months.Count
Retrieve items from List ?
You can retrieve items from List collection by using for loops.
foreach loop
C#
foreach (string month in months)
{
MessageBox.Show(month);
}
VB.Net
For Each month As String In months
MessageBox.Show(month)
Next
for loop
C#
for (int i = 0; i < months.Count; i++)
{
MessageBox.Show(months[i]);
}
VB.Net
For i As Integer = 0 To months.Count - 1
MessageBox.Show(months(i))
Next
Insert an item in the List ?
You can insert an item in the List by specify its index value like (index,item) .
months.Insert(2, "March");
In the above code the month "March" inserted in the index position 2.
Remove an item from List collection ?
Remove() can use to remove item from List collection.
months.Remove("March");
Check if an item contains in the List collection ?
You can use List.Contains() methods to check an item exists in the List
C#
if (months.Contains("March"))
{
MessageBox.Show("The month March exists in the List");
}
VB.Net
If months.Contains("March") Then
MessageBox.Show("The month March exists in the List")
End If
Copy an Array to a List collection ?
C#
string[] strArr = new string[3];
strArr[0] = "Sunday";
strArr[1] = "Monday";
strArr[2] = "Tuesday";
//here to copy array to List
List < string > arrlist = new List < string > (strArr);
VB.Net
Dim strArr As String() = New String(2) {}
strArr(0) = "Sunday"
strArr(1) = "Monday"
strArr(2) = "Tuesday"
'here to copy array to List
Dim arrlist As New List(Of String)(strArr)
Finally clear method remove all the items from List collection.
List.Clear ();
The following program shows some operations in List collections.
Default.aspx
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ListBox ID="ListBox1" runat="server" Height="129px" Width="200px"></asp:ListBox><br />
<br />
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
</div>
</form>
</body>
</html>
Full Source | C#
using System;
using System.Web;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Collections.Generic;
public partial class _Default : System.Web.UI.Page
{
protected void Button1_Click(object sender, EventArgs e)
{
List < string > months = new List < string > ();
//add items in a List collection
months.Add("January");
months.Add("Frebruary");
months.Add("March");
months.Add("April");
months.Add("May");
months.Add("June");
//Remove an Item from list
months.Remove("March");
//insert an item in the list
months.Insert(2, "March");
ListBox1.DataSource = months;
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 months As New List(Of String)()
'add items in a List collection
months.Add("January")
months.Add("Frebruary")
months.Add("March")
months.Add("April")
months.Add("May")
months.Add("June")
'Remove an Item from list
months.Remove("March")
'insert an item in the list
months.Insert(2, "March")
ListBox1.DataSource = months
ListBox1.DataBind()
End Sub
End Class
Click the following links to see full source code
C# Source Code
VB.NET Source Code