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Insert a Default Item When Databinding RadComboBox

This article shows how to add a default item that does not belong to the datasource of a databound RadComboBox. This is useful if you want to add a hint. For example, you can add the Select a country item to a ComboBox that is bound to datasource with countries. The Select a country item will appear as the default item and will remind the users to select a country before continuing.

To add the default item:

  1. Set the AppendDataBoundItems property of the ComboBox to True. This ensures that both databound items and manually inserted items are shown in the dropdown.

  2. Add the static item.

    • You can add the item inline (in the <Items> </Items> section).

    • You can add the item in the code behind. You need to add the item in the DataBound event of the ComboBox (not to be mistaken with ItemDataBound event). The DataBound event fires after all items are bound and loaded to the combobox:

    
    protected void RadComboBox1_DataBound(object sender, EventArgs e) 
    { 
        var combo = (RadComboBox)sender; 
        combo.Items.Insert(0, new RadComboBoxItem("Select a country", string.Empty)); 
    }
    
    ````
    
    
    Protected Sub RadComboBox1_DataBound(ByVal sender As Object, ByVal e As EventArgs)
    
        Dim combo As RadComboBox = DirectCast(sender, RadComboBox)
        combo.Items.Insert(0, New RadComboBoxItem("Select a country", String.Empty))
    
    End Sub
    
    ````
    

    Add a Default Item When Using Templates

If your combobox uses Templates, the template could look like this:

<ItemTemplate>
    <ul>
        <li class="col1"><%# DataBinder.Eval(Container.DataItem, "CompanyName") %></li>
        <li class="col2"><%# DataBinder.Eval(Container.DataItem, "City") %></li>
        <li class="col3"><%# DataBinder.Eval(Container.DataItem, "ContactTitle") %></li>
    </ul>
</ItemTemplate>

Now, if you just add a static item to the combobox - it will not be shown as an item when you open the dropdown. Because its DataItem property is NULL (since it is added as static item) and the DataBinder.Eval() expression returns nothing. Here is what you can do - the following code will insert the Select a country text in the first column of the combobox:

<ItemTemplate>
    <ul>
        <li class="col1"><%# Container.DataItem != null ? DataBinder.Eval(Container.DataItem, "CompanyName") : DataBinder.Eval(Container, "Text") %></li>
        <li class="col2"><%# DataBinder.Eval(Container.DataItem, "City") %></li>
        <li class="col3"><%# DataBinder.Eval(Container.DataItem, "ContactTitle") %></li>
    </ul>
</ItemTemplate>
<Items>
    <telerik:RadComboBoxItem Text="Select a country" />
</Items>

This way, the "Select a country" item will have its DataItem property null, so the dropdown will take its Text property.

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