Migrating from RadComboBox Classic to ASP.NET AJAX version

Updated on Aug 24, 2026

RadComboBox for ASP.NET AJAX has changed because of evolving to the ASP.NET Ajax framework and Telerik.Web.UI suite. All of the client-side properties and methods' names have changed along with several server API changes. Some properties and methods have been completely removed, while new ones have been added.The control's client-side API is not backward-compatible with RadComboBox Classic version. All the changes included in the AJAX RadComboBox's client-side API are listed below:

Client-side API Changes

RadComboBox class

The tlrkComboBoxes array has been removed. The Telerik.Web.UI.RadComboBox.ComboBoxes should be used instead. For more details please refer to the Client-Side Basics article.

 

RadComboBox Classic	RadComboBox AJAX
Methods
HideDropDown	hideDropDown
ToggleDropDown	toggleDropDown
ShowDropDown	showDropDown
Disable	disable
Enable	enable
FindItemByValue	findItemByValue
FindItemByText	findItemByText
GetText / SetText	get_text / set_text
GetValue / SetValue	get_value / set_value
RequestItems	requestItems
ClearItems	clearItems
ClearSelection	clearSelection
ClientDataString	The ClientDataString property has been removed. The OnClientItemsRequesting event's event arguments should be used instead:

ASPNET

	     
function OnClientItemsRequesting(sender, eventArgs)
{    
    //get the context object    
    var context = eventArgs.get_context();    
    //set a value to the context object    
    context["FilterString"] = eventArgs.get_text();  
}
				

Then, you can access the context object in the WebService method:

C#

	     
IDictionary<string, object> contextDictionary = (IDictionary<string, object>) context;
string txt = contextDictionary["FilterString"].ToStrring();
				

You can also access the context object in the ItemsRequested event handler using the event arguments:

C#

	     
protected void RadComboBox1_ItemsRequested(object sender, RadComboBoxItemsRequestedEventArgs e)
{    
    string txt = e.Context["FilterString"].ToString();
}
				

RadComboBox Classic	RadComboBox AJAX
Properties
MoreResultsBoxID	get_moreResultsBoxElement()- returns the DOM element of the MoreResultsBox.
MoreResultsMessageBoxID	get_moreResultsBoxMessageElement() - returns the DOM element of the MoreResultsBox element.
DropDownVisible	get_DropDownVisible()
ImageID	get_imageDomElement() - returns the DOM element of the drop arrow image.
InputID	get_inputDomElement() - returns the DOM element of the input field.
DropDownID	get_dropDownElement()- returns the DOM element of the drop-down area.
Items	get_items() - returns an Items collection.
Enabled	get_enabled() - returns true if the combobox is enabled, false otherwise. set_enabled(true) - enables the RadComboBox, set_enabled(false) - disables the RadComboBox.
SelectedItem	get_selectedItem() / set_selectedItem(item)
HighlightedItem	get_highlightedItem() / set_highlightedItem(item)

RadComboBoxItem class

 

RadComboBoxItem Classic	RadComboBoxItem AJAX
Methods
Highlight	highlight
UnHighlight	unHighlight
Disable	disable
Enable	enable
Select	select
SetAttribute	setAttribute
Properties
Enabled	get_enabled() - returns true if the item is enabled, false otherwise. set_enabled(true) - enables an item, set_enabled(false) - disables an item.
Index	get_index()
ComboBox	get_combobox()
Text	get_text() / set_text(string)
Value	get_value() / set_value(string)

RadComboBoxItemCollection class (new)

Member	Notes
Methods
add	Adds an item
insert	Inserts an item
remove	Removes an item
clear	Clears the items
getItem	Gets an item from the Items collection.
indexOf	Returns the index of an item.
removeAt	Removes an item at a specified index.
get_count	Returns the count of the items.
trackChanges	Indicates the beginning of client-side changes that are meant to be persisted on the server.
commitChanges	Indicates the end of client-side changes that are meant to be persisted on the server.

Server-side API changes

RadComboBox class

 

RadComboBox Classic	Notes
Properties
ContentFile	Removed: The LoadContentFile method should be used instead.
ExternalCallbackPage	Removed: An external streamer page is no longer needed. The items' population of the RadComboBox should be done via WebService instead.
IsCallBack	Removed: The Page.IsCallBack property should be used instead.
Value	Removed: With the new RadComboBox for ASP.NET AJAX , the SelectedValue property is persisted on the server even when the items are loaded on demand. Therefore, the Value property is no longer needed.
RadComboBoxItemsRequestedEventArgs.ClientDataString	Removed: The RadComboBoxItemsRequestedEventArgs.Context property should be used instead. It returns an object of type IDictionary .
AfterClientCallBackError	Changed to OnClientItemsRequestFailed.
Methods
GetXmlString	Changed to GetXml (inherited from ControlItemContainer class).
LoadXmlString	Changed to LoadXml (inherited from ControlItemContainer class).