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Loading Items from a Web Service

Instead of supplying an ItemsRequested event handler to add items on demand to RadComboBox, you can use a Web service to service the items request. The path to the Web service and the name of the service method are specified in the WebServiceSettings' Path and Method properties:

note

RadComboBox input's Text can be obtained from the context object used by the WebService's method. The context object should be cast to IDictionary type, first.


public RadComboBoxItemData[] GetProducts(object context)
{
    IDictionary<string, object> contextDictionary = (IDictionary<string, object>)context;
    //Returns the Text of RadComboBox' input field.
    contextDictionary["Text"].ToString();
    //Returns the value set in the OnClientItemsRequesting event handler.
    contextDictionary["FilterString"].ToString();
}

public RadComboBoxData GetCompanyNames(RadComboBoxContext context)
{
    //Returns the Text of RadComboBox' input field.
    var comboText = context.Text;
}

<script type="text/javascript">
    function OnClientItemsRequesting(sender, eventArgs) {
        var context = eventArgs.get_context();
        context["FilterString"] = eventArgs.get_text();
    }
</script>

<telerik:radcombobox 
    runat="server" 
    id="RadComboBox1" 
    width="300px" 
    enableloadondemand="true"
    onclientitemsrequesting="OnClientItemsRequesting">    
<WebServiceSettings Method="GetProducts" Path="Products.asmx" />
</telerik:radcombobox>

To use the integrated support, the Web service should have the following signature:



[WebMethod]
public RadComboBoxItemData[] GetProducts(object context)
{
    IDictionary<string, object> contextDictionary = (IDictionary<string, object>)context;
    SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString);
    string filterString = ((string)contextDictionary["FilterString"]).ToLower(); 
    SqlCommand selectCommand = new SqlCommand(
 @" SELECT * FROM Customers WHERE LOWER(CompanyName) LIKE '" + filterString + "%'", connection);
    SqlDataAdapter adapter = new SqlDataAdapter(selectCommand); 
    DataTable products = new DataTable(); 
    adapter.Fill(products);
    List<RadComboBoxItemData> result = new List<RadComboBoxItemData>(products.Rows.Count); 
    foreach (DataRow row in products.Rows) 
    { 
        RadComboBoxItemData itemData = new RadComboBoxItemData(); 
        itemData.Text = row["CompanyName"].ToString(); 
        itemData.Value = row["CompanyName"].ToString(); 
        result.Add(itemData); 
    }
    return result.ToArray();
}
[WebMethod]
public RadComboBoxData GetCompanyNames(RadComboBoxContext context)
{    
    //RadComboBoxContext context1 = new JavaScriptSerializer().ConvertToType<RadComboBoxContext>(context);    
    string sql = "SELECT * from Customers WHERE CompanyName LIKE '" + context.Text + "%'";
    SqlDataAdapter adapter = new SqlDataAdapter(sql, ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString); 
    DataTable data = new DataTable(); adapter.Fill(data); 
    List<RadComboBoxItemData> result = new List<RadComboBoxItemData>(context.NumberOfItems); 
    RadComboBoxData comboData = new RadComboBoxData(); 
    try
    {
        int itemsPerRequest = 10; 
        int itemOffset = context.NumberOfItems; 
        int endOffset = itemOffset + itemsPerRequest; 
        if (endOffset > data.Rows.Count) 
        { 
            endOffset = data.Rows.Count; 
        } 
        if (endOffset == data.Rows.Count) 
        { 
            comboData.EndOfItems = true; 
        } 
        else 
        { 
            comboData.EndOfItems = false; 
        }
        result = new List<RadComboBoxItemData>(endOffset - itemOffset);
        for (int i = itemOffset; i < endOffset; i++) 
        { 
            RadComboBoxItemData itemData = new RadComboBoxItemData(); 
            itemData.Text = data.Rows[i]["CompanyName"].ToString(); 
            itemData.Value = data.Rows[i]["CompanyName"].ToString(); 
            result.Add(itemData); 
        }
        if (data.Rows.Count > 0) 
        {
            comboData.Message = String.Format("Items <b>1</b>-<b>{0}</b> out of <b>{1}</b>", endOffset.ToString(), data.Rows.Count.ToString()); 
        } 
        else 
        { 
            comboData.Message = "No matches"; 
        }
    }
    catch (Exception e) 
    { 
        comboData.Message = e.Message; 
    }
    comboData.Items = result.ToArray(); 
    return comboData;
}



<WebMethod()> 
    Public Function GetProducts(ByVal context As Object) As RadComboBoxItemData()
        Dim contextDictionary As IDictionary(Of String, Object) = DirectCast(context, IDictionary(Of String, Object))
        Dim connection As New SqlConnection(ConfigurationManager.ConnectionStrings("NorthwindConnectionString").ConnectionString)
        Dim filterString As String = (DirectCast(contextDictionary("FilterString"), String)).ToLower()
        Dim selectCommand As New SqlCommand("" & Chr(9) & 
    "SELECT * FROM Customers" & Chr(13) & "" & Chr(10) & " WHERE LOWER(CompanyName) LIKE '" + filterString + "%'", connection)
        Dim adapter As New SqlDataAdapter(selectCommand)
        Dim products As New DataTable()
        adapter.Fill(products)
        Dim result As New List(Of RadComboBoxItemData)(products.Rows.Count)
        For Each row As DataRow In products.Rows
            Dim itemData As New RadComboBoxItemData()
            itemData.Text = row("CompanyName").ToString()
            itemData.Value = row("CompanyName").ToString()
            result.Add(itemData)
        Next
        Return result.ToArray()
    End Function
<WebMethod()>

Public Function GetCompanyNames(ByVal context As RadComboBoxContext) As RadComboBoxData

    'RadComboBoxContext context1 = new JavaScriptSerializer().ConvertToType<RadComboBoxContext>(context);
    Dim sql As String = "SELECT * from Customers WHERE CompanyName LIKE '" + context.Text + "%'"
    Dim adapter As New SqlDataAdapter(sql, ConfigurationManager.ConnectionStrings("NorthwindConnectionString").ConnectionString)
    Dim data As New DataTable()
    adapter.Fill(data)
    Dim result As New List(Of RadComboBoxItemData)(context.NumberOfItems)
    Dim comboData As New RadComboBoxData()
    Try
        Dim itemsPerRequest As Integer = 10
        Dim itemOffset As Integer = context.NumberOfItems
        Dim endOffset As Integer = itemOffset + itemsPerRequest
        If endOffset > data.Rows.Count Then
            endOffset = data.Rows.Count
        End If
        If endOffset = data.Rows.Count Then
            comboData.EndOfItems = True
        Else
            comboData.EndOfItems = False
        End If
        result = New List(Of RadComboBoxItemData)(endOffset - itemOffset)
        Dim i As Integer = itemOffset
        While i < endOffset
            Dim itemData As New RadComboBoxItemData()
            itemData.Text = data.Rows(i)("CompanyName").ToString()
            itemData.Value = data.Rows(i)("CompanyName").ToString()
            result.Add(itemData)
            i = i + 1
        End While
        If data.Rows.Count > 0 Then
            comboData.Message = [String].Format("Items <b>1</b>-<b>{0}</b> out of <b>{1}</b>", endOffset.ToString(), data.Rows.Count.ToString())
        Else
            comboData.Message = "No matches"
        End If
    Catch e As Exception
        comboData.Message = e.Message
    End Try
    comboData.Items = result.ToArray()
    Return comboData
End Function

*For a live example refer to the online demo: *Populate From Web Service.

See Also