Binding to RadClientDataSource

This article demonstrates how to bind RadComboBox to RadClientDataSource.

Since Q2 2014 RadComboBox can be bound to a RadClientDataSource control. An important aspect of binding to the RadClientDataSource is that the RadComboBox DataText and DataValue fields should be associated with the custom object properties. Thus you can choose which property value to be shown as RadComboBox item text and value. For reference at the bottom of the web service implementation below you will find the custom class and its properties declaration.

The RadComboBox properties ShowMoreResultBox, ItemsPerRequest and VirtualScrolling work in exactly the same manner as with any other data source control. Some specifics about the load on demand scenarios are listed and explained in the next sections.

When the EnableLoadOnDemand is enabled

The following application scenario shows an example of RadComboBox bound to RadClientDataSource with load on demand.

When the filtering functionality is enabled the default value is "StartsWith". Setting Filter="Contains" will change this behavior.

<telerik:radclientdatasource runat="server" id="ClientDataSource3">
        <DataSource >
            <WebServiceDataSourceSettings BaseUrl="http://url/Service.svc/">
                <Select Url="LoadCustomDataWCF"  DataType="JSON" RequestType="Post" ContentType="application/json; charset=utf-8" />
            </WebServiceDataSourceSettings>
        </DataSource>
        <Schema DataName="d">
        </Schema>
    </telerik:radclientdatasource>

<telerik:radcombobox runat="server" id="Combo1" enableloadondemand="true" enablevirtualscrolling="true" itemsperrequest="10" height="80px" showmoreresultsbox="true"  datatextfield="Name" datavaluefield="Value"
    clientdatasourceid="ClientDataSource3">
</telerik:radcombobox>

[OperationContract]
public CustomData[] LoadCustomDataWCF()
{
    NorthwindReadOnlyDataContext northwind = new NorthwindReadOnlyDataContext();

    //Get all items from the Customers table. This query will not be executed untill the ToArray method is called.
    var allCustomers = (from customer in northwind.Customers
                        orderby customer.ContactName
                        select new CustomData
                        {
                            Name = customer.ContactName,
                            Value = customer.CustomerID
                        }).Take<CustomData>(46);

    var result = allCustomers.ToArray();

    return result;
}

public class CustomData
{
    public string Name { get; set; }
    public string Value { get; set; }

}

Inherits System.Web.UI.Page
<OperationContract> _
Public Function LoadCustomDataWCF() As CustomData()
    Dim northwind As New NorthwindReadOnlyDataContext()

    'Get all items from the Customers table. This query will not be executed untill the ToArray method is called.
Dim allCustomers = (From customer In northwind.CustomersOrder By customer.ContactNameNew CustomData() With { _
    Key .Name = customer.ContactName, _
    Key .Value = customer.CustomerID _
}).Take(Of CustomData)(46)

    Dim result = allCustomers.ToArray()

    Return result
End Function

Public Class CustomData
    Public Property Name() As String
        Get
            Return m_Name
        End Get
        Set(value As String)
            m_Name = Value
        End Set
    End Property
    Private m_Name As String
    Public Property Value() As String
        Get
            Return m_Value
        End Get
        Set(value As String)
            m_Value = Value
        End Set
    End Property
    Private m_Value As String

End Class

When the EnableLoadOnDemand is disabled

The code snippet below shows a sample configuration of RadComboBox bound to RadClientDataSource with virtual scrolling.

In this case it is necessary initially to request the items using the RadComboBox client-side API method requestItems("") and passing empty string as parameter. For reference please take a look at the code snippets below:

<telerik:radclientdatasource runat="server" id="ClientDataSource5">
         <DataSource >
            <WebServiceDataSourceSettings BaseUrl="http://url/Service.svc/">
                <Select Url="LoadCustomDataWCF"  DataType="JSON" RequestType="Post" ContentType="application/json; charset=utf-8" />
            </WebServiceDataSourceSettings>
        </DataSource>
        <Schema DataName="d">
        </Schema>
    </telerik:radclientdatasource>
<telerik:radcombobox runat="server" id="Combo2" enablevirtualscrolling="true" itemsperrequest="10" height="80px" showmoreresultsbox="true" datatextfield="Name" datavaluefield="Value" onclientdropdownopening="onClientDropDownOpening"
    clientdatasourceid="ClientDataSource5">
</telerik:radcombobox>

<script type="text/javascript">
    var $ = $telerik.$,
        isLoaded = false;

    function onClientDropDownOpening(sender, args) {
        if (!isLoaded) {
            sender.requestItems("");

            isLoaded = true;
        }
    }

</script>

[OperationContract]
public CustomData[] LoadCustomDataWCF()
{
NorthwindReadOnlyDataContext northwind = new NorthwindReadOnlyDataContext();

    //Get all items from the Customers table. This query will not be executed untill the ToArray method is called.
    var allCustomers = (from customer in northwind.Customers
                        orderby customer.ContactName
                        select new CustomData
                        {
                            Name = customer.ContactName,
                            Value = customer.CustomerID
                        }).Take<CustomData>(46);

    var result = allCustomers.ToArray();

    return result;
}

public class CustomData
{
    public string Name { get; set; }
    public string Value { get; set; }

}

Inherits System.Web.UI.Page
<OperationContract> _
Public Function LoadCustomDataWCF() As CustomData()
    Dim northwind As New NorthwindReadOnlyDataContext()

    'Get all items from the Customers table. This query will not be executed untill the ToArray method is called.
Dim allCustomers = (From customer In northwind.CustomersOrder By customer.ContactNameNew CustomData() With { _
    Key .Name = customer.ContactName, _
    Key .Value = customer.CustomerID _
}).Take(Of CustomData)(46)

    Dim result = allCustomers.ToArray()

    Return result
End Function

Public Class CustomData
    Public Property Name() As String
        Get
            Return m_Name
        End Get
        Set(value As String)
            m_Name = Value
        End Set
    End Property
    Private m_Name As String
    Public Property Value() As String
        Get
            Return m_Value
        End Get
        Set(value As String)
            m_Value = Value
        End Set
    End Property
    Private m_Value As String

End Class