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The filtering functionality is enabled through the Filter property. The following values could be assigned:

  • None - this is the default value. No filtering is performed.

  • Contains - returns all items which Texts' values contain the searched text as a substring:

ComboBox Filter Contains

  • StartsWith - returns all items which texts start with the searched text:

ComboBox Filter Starts With

  • Filtering is NOT case sensitive;
  • CheckBox functionality is NOT supported in combination with filtering. The reason is that the CheckBox selection is different from the standard RadComboBox's selection - there is no single selected item.

Setting the Filter server-side

protected void Page_Load(object sender, EventArgs e) 
    RadComboBox1.Filter = RadComboBoxFilter.StartsWith; 

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    RadComboBox1.Filter = RadComboBoxFilter.StartsWith

End Sub

Setting the Filter inline

<telerik:radcombobox id="RadComboBox1" filter="Contains" runat="server"></telerik:radcombobox>

Controlling the appearance of the Filter

To control the appearance of the filtered items (their <EM> elements), the following CSS classes should be altered:

<style type="text/css">
    div.RadComboBoxDropDown_Sunset em
        font-style: normal;
        font-weight: bold;
    div.RadComboBoxDropDown_Sunset .rcbItem em
        background: Yellow;

Sunset is the name of the Skin that the RadComboBox is currently using. You need to change it with the name of the skin that you use.

The result is:

ComboBox Filter Styled

If you use ItemsTemplate the filtering will still work, but the matching text portion will not be highlighted (the <EM> element will be not added).

How does the filtering work?

When you enable filtering (by setting the Filter property to either Contains or StartsWith) and you start typing in the input area of the combobox, the items that do not match are hidden by the client-side function set_visible(false). They are visually invisible, but they do persist on the server. The items that do match the search text have <EM> element added within their text.

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