RadControls for ASP.NET AJAX HeaderTemplate element of the RadComboBox, allows the header of the items in the drop-down list, to be customized.
The header is especially useful if your item template displays attributes in multiple columns, although it can be used with any RadComboBox item style.
It could be used even when RadComboBox does not have an ItemTemplate defined. Like the ItemTemplate,
the HeaderTemplate can include any HTML element.
The following example shows how to create a multi-column RadComboBox with a header that labels the columns of each item.
 Note |
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Both, the HeaderTemplate and ItemTemplate, lay out items using a
table that fixes column width, so that the header and items line up properly.
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Defining HeaderTemplates inline
CopyASPX
<telerik:radcombobox
id="RadComboBox1"
runat="server"
height="190px"
width="420px"
markfirstmatch="true"
datasourceid="MyDataSource"
highlighttemplateditems="true"
onitemdatabound="RadComboBox1_ItemDataBound">
<HeaderTemplate>
<table style="width: 415px; text-align: left">
<tr>
<td style="width: 125px;">Company Name</td>
<td style="width: 125px;">City</td>
<td style="width: 125px;">Title</td>
<td style="width: 40px;" align="right">
<img alt="" src="img/help.gif" />
</td>
</tr>
</table>
</HeaderTemplate>
<ItemTemplate>
<table style="width: 415px; text-align: left">
<tr>
<td style="width: 125px;">
<%# DataBinder.Eval(Container.DataItem"CompanyName") %>
</td>
<td style="width: 125px;">
<%# DataBinder.Eval(Container.DataItem"City") %>
</td>
<td style="width: 125px;">
<%# DataBinder.Eval(Container.DataItem"ContactTitle") %>
</td>
<td style="width: 40px;"></td>
</tr>
</table>
</ItemTemplate>
</telerik:radcombobox>ItemDataBound
CopyC#
protected void RadComboBox1_ItemDataBound(object sender, RadComboBoxItemEventArgs e)
{
e.Item.Text = ((DataRowView)e.Item.DataItem)["CompanyName"].ToString() + "; " +
((DataRowView) e.Item.DataItem)["City"].ToString() + "; " +
((DataRowView)e.Item.DataItem)["ContactTitle"].ToString();}CopyVB.NET
Protected Sub RadComboBox1_ItemDataBound(ByVal sender As Object, ByVal e As RadComboBoxItemEventArgs)
e.Item.Text = (DirectCast(e.Item.DataItem, DataRowView))("CompanyName").ToString() + "; " +
(DirectCast(e.Item.DataItem, DataRowView))("City").ToString() + "; " +
(DirectCast(e.Item.DataItem, DataRowView))("ContactTitle").ToString()
End SubThe result looks as follows:
Defining HeaderTemplates at run-time
CopyASPX
<telerik:radcombobox
id="RadComboBox1"
runat="server"
radcomboboximageposition="Right"
autopostback="true">
</telerik:radcombobox>CopyC#
protected override void OnInit(EventArgs e)
{
RadComboBox1.HeaderTemplate = new HeaderTemplate();
base.OnInit(e);
}
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
RadComboBox1.Items.Add(new RadComboBoxItem("RadComboBoxItem4"));
RadComboBox1.Items.Add(new RadComboBoxItem("RadComboBoxItem5"));
}
RadComboBox1.DataBind();
}
class HeaderTemplate : ITemplate
{
public void InstantiateIn(Control container)
{
HtmlTable table = new HtmlTable();
HtmlTableRow row = new HtmlTableRow();
HtmlTableCell cell = new HtmlTableCell();
cell.InnerText = "Value";
row.Controls.Add(cell);
HtmlTableCell cell1 = new HtmlTableCell();
cell1.InnerText = "Text";
row.Controls.Add(cell1);
table.Controls.Add(row);
container.Controls.Add(table);
}
}CopyVB.NET
Protected Overloads Overrides Sub OnInit(ByVal e As EventArgs)
RadComboBox1.HeaderTemplate = New HeaderTemplate()
MyBase.OnInit(e)
End Sub
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
If Not Page.IsPostBack Then
RadComboBox1.Items.Add(New RadComboBoxItem("RadComboBoxItem4"))
RadComboBox1.Items.Add(New RadComboBoxItem("RadComboBoxItem5"))
End If
RadComboBox1.DataBind()
End Sub
Class HeaderTemplate Implements ITemplate
Public Sub InstantiateIn(ByVal container As Control) Implements ITemplate.InstantiateIn
Dim table As New HtmlTable()
Dim row As New HtmlTableRow()
Dim cell As New HtmlTableCell()
cell.InnerText = "Value"
row.Controls.Add(cell)
Dim cell1 As New HtmlTableCell()
cell1.InnerText = "Text"
row.Controls.Add(cell1)
table.Controls.Add(row)
container.Controls.Add(table)
End Sub
End ClassAccessing controls in HeaderTemplate
You can find any control embedded in the RadComboBox' HeaderTemplate, like:
CopyC#
Button btn = (Button)RadComboBox1.Header.FindControl("Button1");
btn.Text = "New Text";CopyVB.NET
Dim btn As Button = CType(RadComboBox1.Header.FindControl("Button1"), Button)
btn.Text = "New Text"See Also