Skip to main content
Tab

ASPxComboBox Class

An editor which displays a list of items within its dropdown window.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v21.2.dll

Declaration

public class ASPxComboBox :
    ASPxAutoCompleteBoxBase,
    IListBoxColumnsOwner,
    IValueTypeHolder,
    IControlDesigner,
    IListEditItemRequestEventOwner,
    IListEditCustomFilteringEventOwner,
    IListEditServerModeOwner

Remarks

The ASPxComboBox control combines the functionality of a text editor, button editor, and drop-down list editor. The editor’s drop-down menu displays a list of items that users can select.

ASPxComboBox Control

Run Demo

Create a ComboBox Control

Design Time

The ASPxComboBox control is available on the DX.21.2: Common Concepts toolbox tab in the Microsoft Visual Studio IDE.

ComboBox in Toolbox

Drag the control onto a form and customize the control’s settings, or paste the control’s markup in the page’s source code.

<dx:ASPxComboBox ID="ASPxComboBox1" runat="server">
</dx:ASPxComboBox>

Run Time

using DevExpress.Web;
//...
protected void Page_Load(object sender, EventArgs e) {
    ASPxComboBox comboBox = new ASPxComboBox();
    comboBox.ID = "ASPxComboBox1";
    // Add the created control to the page
    Page.Form.Controls.Add(comboBox);
}

Client-Side API

Availability

Set the ASPxEditBase.EnableClientSideAPI property to true or handle any client event.

Client object type

ASPxClientComboBox

Access name

ASPxEditBase.ClientInstanceName

Events

ASPxComboBox.ClientSideEvents

Run Demo: Cascading Combo Boxes

Bind to Data

The ASPxAutoCompleteBoxBase.Items collection contains the ASPxComboBox‘s items. You can access an individual item and specify its properties (ListEditItem).

The ASPxComboBox automatically binds its items to data if the data source fields are named in the same way as the item properties (Text, Name, ImageUrl). Otherwise, you should specify these properties:

Name

Description

ImageUrlField

Specifies the data source field that contains the image location for the editor’s items.

TextField

Specifies the data source field that contains texts to display in the dropdown.

ValueField

Specifies the data source field that contains values for the editor’s items.

<dx:ASPxComboBox ID="ASPxComboBox1" runat="server" 
    DataSourceID="ProductsDataSource" TextField="ProductName" ValueField="ProductName">
    <!--...-->
</dx:ASPxComboBox>
<ef:EntityDataSource runat="server" ID="ProductsDataSource" ... />

Run Demo: Bind to Data

See also: How to bind the ASPxComboBox to a data source

Database Server Mode

In this mode, the editor loads only required (visible) items to the server memory and executes data operations (for instance, filtering) at the data source level. The GridViewDataComboBoxColumn object does not support database server mode.

Bind the ASPxComboBox to the LinqServerModeDataSource or EntityServerModeDataSource and set the EnableCallbackMode property to true to enable the database server mode.

Run Demo: Database Server Mode

See also: Binding to Large Data

Item Load Modes

The ASPxComboBox supports the following load modes:

Load Mode

Description

Affected Properties

Default

The editor loads items and executes all data operations (for instance, scrolling, filtering, and so on) on the client without a round trip to the server.

EnableCallbackMode=”False”

On-Demand

You can use callbacks to load items from the server on demand. For instance, the editor can dynamically load non-displayed items when a user scrolls the dropdown.

EnableCallbackMode = “True”

Dynamic

You can manually populate a dropdown list with the required items based on the filter criteria and a user’s scroll action.

EnableCallbackMode=”True”

ASPxComboBox - Item Load Mode

<dx:ASPxComboBox ID="ASPxComboBox1" runat="server"  EnableCallbackMode="true" CallbackPageSize="30" 
    DataSourceID="SqlDataSource1" ValueField="ShipName" TextField="ShipName">
</dx:ASPxComboBox>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ...></asp:SqlDataSource>

See also: Item Load Modes

Incremental Filtering

Use the ASPxAutoCompleteBoxBase.IncrementalFilteringMode property to enable the control to filter data while a user types the filter string.

Filter Mode

Description

StartsWith

The editor filters items that begin with the filter string.

Contains

The editor filters items that contain the filter string.

ComboBox-IncrementalFilteringMode-StartsWith

<dx:ASPxComboBox ID="Countries" runat="server" EnableCallbackMode="True" IncrementalFilteringMode="StartsWith">
    <Items>
        <!--...-->
    </Items>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Incremental Filtering

You can also use the following properties:

Property

Description

ASPxAutoCompleteBoxBase.IncrementalFilteringDelay

Specifies the time interval after which the editor filters items.

ASPxAutoCompleteBoxBase.FilterMinLength

Specifies the minimum filter string length to filter items.

See also: Incremental Filtering

Custom Filtering

You can filter items by multiple words and columns, or use diacritic characters in the filter string.

ASPxComboBox-CustomFiltering

<dx:ASPxComboBox ID="CmbWithClientFiltering" runat="server" ValueField="Name" TextField="Name" DataSourceID="GermanCitiesDataSource" IncrementalFilteringMode="Contains">
    <ClientSideEvents ItemFiltering="onItemFiltering" CustomHighlighting="onCustomHighlighting" />
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Custom Filtering

See also: Custom Filtering

Display Format

You can specify indexed placeholders (such as “{0}”, “{1}”, and so on) and literals for the following properties to customize the text of the ASPxComboBox‘s edit box:

Property

Description

ASPxAutoCompleteBoxBase.TextFormatString

Defines a pattern to display the selected item’s text when there are several columns in the dropdown.

ASPxTextEdit.DisplayFormatString

Defines the pattern applied to the editor’s value.

ASPxComboBox - Display Formatting

<dx:ASPxComboBox ID="ASPxComboBox4" runat="server" DataSourceID="EmployeesDataSource" 
                 TextFormatString="{0} from {2}" ValueField="EmployeeID">
    <Columns>
        <!--...-->
    </Columns>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Display Format

Multi-Column Mode

The ASPxComboBox allows you to display a collection of data source fields as multiple columns in the drop-down list.

In design mode, invoke the Designer… and select the Columns… item from the smart tag menu to add and configure columns. Alternatively, you can use the ASPxComboBox.Columns property to access the editor’s columns collection. Specify the ListBoxColumn.FieldName property to bind the column’s items to a data source field.
You can also specify header caption, width, visibility state, and other settings for columns.

ASPxComboBox_MultiColumns.png

<dx:ASPxComboBox ID="CmbCustomers" runat="server" DataSourceID="CustomersDataSource" ValueField="CustomerID" ValueType="System.String" TextFormatString="{0}" EnableCallbackMode="true">
    <Columns>
        <dx:ListBoxColumn FieldName="ContactName" />
        <!--...-->
    </Columns>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Multi-Column Mode

See also: List Editors in Multi-Column Mode

Item Images

The ASPxComboBox‘s drop-down window can display items with associated images.

Property

Description

ASPxAutoCompleteBoxBase.ItemImage

Specifies a uniform image for all editor’s items.

ListEditItem.ImageUrl

Specifies an image for an individual item.

ASPxAutoCompleteBoxBase.ImageUrlField

Specifies a data field that contains image URLs.

ASPxComboBox_concepts4

<dx:ASPxComboBox ID="ASPxComboBox2" runat="server" ShowImageInEditBox="True">
    <ItemImage Height="24px" Width="23px" />
    <Items>
        <dx:ListEditItem Text="Manhattan Bar" ImageUrl="your path" />
        <!--...-->
    </Items>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Item Images

Item Appearance Customization

The ASPxComboBox allows you to customize item appearance. Use the ItemTextCellPrepared and ItemRowPrepared events to specify the style of the drop-down window’s cells and rows.

ASPxComboBox-ItemAppearanceCustomization

<dx:ASPxComboBox ID="customersComboBox" runat="server" DataSourceID="CustomersDataSource" ValueField="CustomerID" ValueType="System.String" TextFormatString="{0}" EnableCallbackMode="true" OnItemTextCellPrepared="customersComboBox_ItemTextCellPrepared" OnItemRowPrepared="customersComboBox_ItemRowPrepared">
    <Columns>
        <dx:ListBoxColumn FieldName="ContactName" />
        <dx:ListBoxColumn FieldName="CompanyName" />
        <dx:ListBoxColumn FieldName="Phone" />
    </Columns>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Item Appearance Customization

Item Template

Use the ASPxAutoCompleteBoxBase.ItemTemplate property to define a custom layout for the editor’s items.

ASPxComboBox-ItemTemplate

<dx:ASPxComboBox ID="ComboBox" EnableCallbackMode="true" DataSourceID="ContactsDataSource" TextField="Name" runat="server">
    <ItemTemplate>
        <table>
            <tr>
                <td rowspan="2">
                    <div class="frame">
                        <img class="photo" alt="photo" src="<%# Page.ResolveUrl(Eval("PhotoUrl").ToString()) %>" />
                    </div>
                </td>
                <!--...-->
        </table>
    </ItemTemplate>
</dx:ASPxComboBox>

Run Demo: ASPxComboBox - Item Template

Customizable Button Collection

The ASPxComboBox contains an edit button collection (EditButtonCollection) that allows you to define button appearance and handle its events. You can also customize the DropDownButton‘s settings.

ASPxComboBox_concepts5

<dx:ASPxComboBox ID="ASPxComboBox" runat="server">
    <Buttons>
        <dx:EditButton Text="Previous" Position="Left" />
        <dx:EditButton Text="Next" Position="Right" />
    </Buttons>
</dx:ASPxComboBox>

See also: EditButton

Built-in Validation

The ASPxComboBox supports the client-side and server-side validation.

The control allows you to define validation rules in the following ways:

<dx:ASPxComboBox ID="ASPxComboBox" runat="server" DataSourceID="SqlDataSource1" TextField="City" ValueField="City" >
    <ValidationSettings ErrorTextPosition="Bottom" Display="Dynamic">
        <RequiredField IsRequired="True" ErrorText="Select a city!" />
    </ValidationSettings>
</dx:ASPxComboBox>

ASPxComboBox-Validation

Run Demo: Inplace Validation

See also: Validation

See Also