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Version Q2 2011 released 07/12/2011
select

ComboBox / Automatic Load On Demand

Configuration
Filter:
EntityDataSource:

LinqDataSource:

  • RadComboBox supports codeless or Automatic Load On Demand with all kinds of data sources including .NET 3.5's Linq and EntityDataSource.

    Setting up the automatic Load On Demand is straightforward:

    • Set the DataSourceID property to the ID of the data source and the DataTextField and DataValueField properties to the respective fields in the data items returned by it.
    • Set EnableAutomaticLoadOnDemand to true.
    • (Optional) Set ShowMoreResultsBox/EnableVirtualScrolling to true to enable the respective features.
    • (Optional) Set ItemsPerRequest to the number of Items you would like to load per request. The default (-1) loads all Items at once.

    Note: When you use the DataSourceID or DataSource properties to bind RadComboBox during automatic Load On Demand the ItemDataBound event fires normally, which means that you can use it to change the Item's Text and Value properties as well as modify its Attributes collection based on the DataItem, etc.

Source Code

C# VB.NET
Show code in new window Demo isolation steps
  • <%@ Page Language="C#" AutoEventWireup="true" CodeFile="DefaultCS.aspx.cs" Inherits="DefaultCS" %>

    <%@ Register Assembly="System.Web.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
        Namespace="System.Web.UI.WebControls" TagPrefix="asp" %>
    <%@ Register TagPrefix="qsf" Namespace="Telerik.QuickStart" %>
    <%@ Register TagPrefix="qsf" TagName="Header" Src="~/Common/Header.ascx" %>
    <%@ Register TagPrefix="qsf" TagName="HeadTag" Src="~/Common/HeadTag.ascx" %>
    <%@ Register TagPrefix="qsf" TagName="Footer" Src="~/Common/Footer.ascx" %>
    <%@ Register TagPrefix="telerik" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head runat="server">
        <title>Untitled Page</title>
        <qsf:HeadTag runat="server" ID="Headtag1"></qsf:HeadTag>
        <!-- custom head section -->
        <style type="text/css">
            span.text
            {
                float: left;
                font: 13px 'Segoe UI' , Arial, sans-serif;
                color: #4888a2;
                display: block;
                width: 150px;
                padding: 2px 20px 0 0;
            }
            
            .qsfConfig input
            {
                margin-left: 50px;
                position: relative;
                top: 1px;
            }
        </style>
        
        <link href="styles.css" rel="stylesheet" type="text/css" />
        <!-- end of custom head section -->
    </head>
    <body class="BODY">
        <form id="mainForm" method="post" runat="server">
        <telerik:RadScriptManager ID="RadScriptManager1" runat="server" />
        <qsf:Header ID="Header1" runat="server" NavigationLanguage="C#"></qsf:Header>
        <telerik:RadAjaxPanel ID="RadAjaxPanel1" runat="server">
        <qsf:ConfiguratorPanel runat="server" ID="ConfigurationPanel1" Title="Configuration" Expanded="true">
            <span class="title">Filter:</span>
            <asp:RadioButton ID="FilterStartsWith" runat="server" AutoPostBack="true" Text="StartsWith" Checked="true" GroupName="Filter" />
            <asp:RadioButton ID="FilterContains" runat="server" AutoPostBack="true" Text="Contains" GroupName="Filter" />
        </qsf:ConfiguratorPanel>
        <!-- content start -->
        <span class="text">EntityDataSource: </span>
        <telerik:RadComboBox ID="RadComboBox1" runat="server" Height="180px" Width="220px"
            DataSourceID="EntityDataSource1" DataTextField="ContactName" DataValueField="ContactName"
            EnableAutomaticLoadOnDemand="true" ShowMoreResultsBox="true" EnableVirtualScrolling="true"
            ItemsPerRequest="10">
        </telerik:RadComboBox>
    <asp:EntityDataSource ID="EntityDataSource1" runat="server" ConnectionString="name=NorthwindEntities"
    DefaultContainerName="NorthwindEntities" EntitySetName="Customers" Select="it.[ContactName]"
    AutoPage="true" OrderBy="it.[ContactName]">
        </asp:EntityDataSource>
        <br />
        <br />
        <span class="text">LinqDataSource: </span>
        <telerik:RadComboBox ID="RadComboBox2" runat="server" Height="180px" Width="220px"
            DataSourceID="LinqDataSource1" DataTextField="ContactName" DataValueField="ContactName"
            EnableAutomaticLoadOnDemand="true" ItemsPerRequest="10" ShowMoreResultsBox="true"
            EnableVirtualScrolling="true">
        </telerik:RadComboBox>
    <asp:LinqDataSource runat="server" ID="LinqDataSource1" ContextTypeName="LinqToSql.NorthwindDataContext"
    OrderBy="ContactName" Select="new (ContactName)" TableName="Customers">
        </asp:LinqDataSource>
        <!-- content end -->
        </telerik:RadAjaxPanel>
        <qsf:Footer runat="server" ID="Footer1"></qsf:Footer>
        </form>
    </body>
    </html>

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