Class DynamicListBox

A ListBox which can retrieve and persist any client-side changes to its Items collection.

Inheritance

System.Object

DynamicListBox

Implements

System.Web.UI.IPostBackDataHandler

System.Web.UI.INamingContainer

Namespace: Mediachase.Web.Console.Controls

Assembly: Mediachase.WebConsoleLib.dll

Version: 10.8.0

Syntax

public class DynamicListBox : ListBox, IPostBackDataHandler, INamingContainer

Remarks

In order for your client-side changes to be persisted, you must call new javascript methods on the ListBox. This Select element now has "Add" and "Remove" methods. The Add method takes the value, text, and optional index of the new ListItem. The Remove method takes the index of the ListItem to remove.

By default, the clientscript used by the control is emited directly into the page. In order to save bandwidth, it's possible to have the control to use a script reference instead, but this requires the following handler to be added to the httpHandlers section of web.config.

<httpHandlers>
	<add verb="*"
		path="MetaBuilders_WebControls_DynamicListBoxResourceHandler.axd"
		type="MetaBuilders.WebControls.DynamicListBoxResourceHandler,MetaBuilders.WebControls.DynamicListBox"
		validate="false"
	/>
</httpHandlers>

Examples

The following is an example of how to combine the DynamicListBox with client-script in your page.

<%@ Page Language="C#" %>
<%@ Register TagPrefix="mb" Namespace="MetaBuilders.WebControls" Assembly="MetaBuilders.WebControls.DynamicListBox" %>
<script runat="server">

	protected void Page_Load( Object sender, EventArgs e ) {
		RegisterClientScriptBlock( MyList.ClientID, "<script>\r\nwindow.MyListId='" + MyList.ClientID + "';\r\n</" + "script>");
	}
    protected void MyList_ListChanged( Object sender, EventArgs e ) {
        if( MyList.SelectedIndex == -1 ) {
            Result.Text = "The SelectedIndex changed and now nothing on the list is selected";
        } else {
            Result.Text = "The SelectedIndex changed and is now '" + MyList.SelectedIndex + "'<br>The selected item is: " + MyList.SelectedItem.Value + "/" + MyList.SelectedItem.Text;
        }
    }

</script>
<html><body><form runat="server">

    <mb:DynamicListBox id="MyList" runat="server" OnSelectedIndexChanged="MyList_ListChanged" SelectionMode="Multiple" >
        <asp:ListItem value="normalItem1" text="normalItem1"></asp:ListItem>
        <asp:ListItem value="normalItem2" text="normalItem2"></asp:ListItem>
    </mb:DynamicListBox>

    <br><br>
    <a href="javascript:remove();" >Remove</a>
    <a href="javascript:add();" >Add</a>
    <script>
		function remove() {
			var list = DynamicListBox_FindControl(window.MyListId);
			var keepLooking = true;
			while ( keepLooking ) {
				list.Remove( list.options.selectedIndex );
				if ( list.options.selectedIndex < 0 ) {
					keepLooking = false;
				}
			}
		}

		function add() {
			var list = DynamicListBox_FindControl(window.MyListId);
			var generatedName = "newItem" + ( list.options.length + 1 );
			list.Add(generatedName,generatedName);
		}
    </script>

    <br><br>
    <asp:Button runat="server" text="Smack"/>

    <br><br>
    <asp:Label runat="server" id="Result" />

</form></body></html>

Constructors

DynamicListBox()

Declaration

public DynamicListBox()

Properties

Controls

Overridden to call EnsureChildControls.

Declaration

public override ControlCollection Controls { get; }

Property Value

Type	Description
System.Web.UI.ControlCollection

Remarks

Supposedly should be done for all controls which override CreateChildControls

Methods

CreateChildControls()

Overridden to include the hidden input which tracks the client side changes.

Declaration

protected override void CreateChildControls()

OnItemsChanged(EventArgs)

Raises the ItemsChanged event.

Declaration

protected virtual void OnItemsChanged(EventArgs e)

Parameters

Type	Name	Description
System.EventArgs	e	The System.EventArgs instance containing the event data.

OnPreRender(EventArgs)

Overridden to register client script.

Declaration

protected override void OnPreRender(EventArgs e)

Parameters

Type	Name	Description
System.EventArgs	e	An System.EventArgs object that contains the event data.

RegisterArrayScript()

Declaration

protected virtual void RegisterArrayScript()

RegisterClientScript()

Registers all the client script for the DynamicListBox

Declaration

protected virtual void RegisterClientScript()

RegisterLibraryScript()

Registers the library script for the DynamicListBox

Declaration

protected virtual void RegisterLibraryScript()

RegisterStartupScript()

Registers the DynamicListBox startup script

Declaration

protected virtual void RegisterStartupScript()

RenderEndTag(HtmlTextWriter)

Overridden to render children after the end tag.

Declaration

public override void RenderEndTag(HtmlTextWriter writer)

Parameters

Type	Name	Description
System.Web.UI.HtmlTextWriter	writer	A System.Web.UI.HtmlTextWriter that represents the output stream to render HTML content on the client.

Events

ItemsChanged

The event that is raised when the user has changed the listbox's items collection..

Declaration

public event EventHandler ItemsChanged

Event Type

Type	Description
System.EventHandler

Implements

System.Web.UI.IPostBackDataHandler

System.Web.UI.INamingContainer