ListBox

The Wisej.Web.ListBox control displays a list of strings or data-bound values, allowing the user to select one or multiple options.

Features

Label

The ListBox control supports the inline Label property. This allows an application to set a label in relation to a ListBox control without having to create an additional Label control.

Data Binding

Data binding is fully supported, including formatting and conversion of the value, through the default data binding infrastructure.

In addition to binding the value (Text, or SelectedItem or SelectedValue bindable properties), the ListBox control also supports data binding to populate the list using the DataSource property in conjunction with the DisplayMember, ValueMember, ToolTipMember and IconMember properties.

When the ShowToolTips property is set to true, the ComboBox control uses the name specified in the ToolTipMember to read the tooltip text to display next to each item in the drop down list.

Selection Modes

The ListBox control allows users to define one of several different selection modes for the control's configuration.

You can see the different configuration options shown below.

Lazy Loading

The ListBox control includes lazy loading support. Lazy loading works by sending the minimum number of records to the browser that is required for display within the control.

Lazy loading will significantly reduce waiting times related to rendering on the browser and network congestion caused by transferring large datasets from the server to the client (browser).

Virtual Scrolling

The ListBox control has the ability to use virtual scrolling, a feature that only renders the list items currently visible in the browser.

Using this option can drastically reduce the amount of time spent rendering in the browser for large datasets. For a List containing 25,000 strings, the effect will be a noticeable difference of several seconds.

Try the following sample code to test the loading times:

private void Page1_Load(object sender, EventArgs e)
{
	var myList = new List<string>();
	
	for (int i=0; i<25000; i++)
	{
		myList.Add($"String {i}");
	}

	this.listBox1.VirtualScroll = true;
	this.listBox1.DataSource = myList;
}

Private Sub Page1_Load(object sender, EventArgs e) Handles Page1.Load

	Dim myList As New List(Of String)
	
	For i = 0 To 25000
		myList.Add($"String {i}")
	Next

	Me.listBox1.VirtualScroll = true
	Me.listBox1.DataSource = myList
	
End Sub

How To

Populate a List

There are a few different ways to populate a ListBox control.

You can add a list of strings using the Items property of the ListBox control.

private void button1_Click(object sender, EventArgs e)
{
	this.listBox1.Items.AddRange(new[] {
		"Eggs",
		"Milk",
		"Carrots"
	});
}

Option Strict Off

Private Sub Button1_Click(sender as Object, e As EventArgs) Handles Button1.Click

	Me.listBox1.Items.AddRange({
		"Eggs",
		"Milk",
		"Carrots"
	})
	
End Sub

Alternatively, you can assign a list of items using the DataSource property of the control.

private void button1_Click(object sender, EventArgs e)
{
	var myList = new List<dynamic>()
	{
		new { id = 1, name = "John" },
		new { id = 2, name = "Jane" },
		new { id = 3, name = "Sally" }
	};

	this.listBox1.ValueMember = "id";
	this.listBox1.DisplayMember = "name";
	
	this.listBox1.DataSource = myList;
}

Option Strict Off

Private Sub Button1_Click(sender as Object, e As EventArgs) Handles Button1.Click
{
	Dim myList As New List(Of Object) From
	{
		New With { .id = 1, .name = "John"},
		New With { .id = 2, .name = "Jane"},
		New With { .id = 3, .name = "Sally"}
	}

	Me.listBox1.ValueMember = "id"
	Me.listBox1.DisplayMember = "name"
	Ne.listBox1.DataSource = myList
	
End Sub

Add an Icon

Icon

Building off of the previous code snippet, it is easy to add an icon to the ListBox items.

private void button1_Click(object sender, EventArgs e)
{
	var myList = new List<dynamic>()
	{
		new { id = 1, name = "John", icon = "Images/People/1.png" },
		new { id = 2, name = "Jane", icon = "Images/People/2.png" },
		new { id = 3, name = "Sally", icon = "Images/People/3.png" }
	};

	this.listBox1.IconMember = "icon";
	this.listBox1.DisplayMember = "name";
	this.listBox1.DataSource = myList;
}

Option Strict Off

Private Sub Button1_Click(sender as Object, e As EventArgs) Handles Button1.Click
{
	Dim myList As New List(Of Object) From
	{
		New With { .id = 1, .name = "John", .icon = "Images/People/1.png" },
		New With { .id = 2, .name = "Jane", .icon = "Images/People/2.png" },
		New With { .id = 3, .name = "Sally", .icon = "Images/People/3.png" }
	}

	Me.listBox1.IconMember = "icon"
	Me.listBox1.DisplayMember = "name"
	Ne.listBox1.DataSource = myList
	
End Sub

The icon paths specified in each object refer to the location of the image relative to the root of the project.

The above code will result in something similar to the following:

Format a String

If you are working currencies, dates, or other forms of data, you might want to utilize the FormatString property of the ListBox control.

private void button1_Click(object sender, EventArgs e)
{
	var myList = new List<dynamic>()
	{
		new { id = 1, name = "John", payment = 32.53 },
		new { id = 2, name = "Jane", payment = 235.53 },
		new { id = 3, name = "Sally", payment = 45.21 }
	};

	this.listBox1.FormatString = "C2";
	this.listBox1.FormattingEnabled = true;
	this.listBox1.DisplayMember = "payment";
	this.listBox1.DataSource = myList;
}

Option Strict Off

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

	Dim myList As New List(Of Object) From
	{
		New With { .id = 1, .name = "John", .payment = 32.53 }
		New With { .id = 2, .name = "Jane", .payment = 235.53 }
		New With { .id = 3, .name = "Sally", .payment = 45.21 }
	}

  Me.listBox1.FormatString = "C2"
	Me.listBox1.FormattingEnabled = true
	Me.listBox1.DisplayMember = "payment"
	Me.listBox1.DataSource = myList
	
End Sub

The result will look something like this (dependent on system currency):

Advanced

JavaScript Widget