Today I discovered the simplest and most elegant solution I’ve seen to date. One line of code in the code behind file is still required, but the elegance of DataSource controls is kept. In short, once the DropDownList has bound to its data source, add the “Choose xxxxx” item to the items collection of the DropDownList. The trick is to use the Insert method instead of the Add method, since the Insert method allows you to specify where the new item should be inserted, and not just added to the end of the item list.

In this example I use the OnDataBound event to insert the new item:

<asp:DropDownList ID="ddlCustomer" runat="server" 
    DataSourceID="odsCustomer" DataTextField="DisplayName" 
    DataValueField="CustomerId" OnDataBound="ddlCustomer_DataBound">
</asp:DropDownList>

The code behind is just one line of code (excluding the method definition):

protected void ddlCustomer_DataBound(object sender, EventArgs e)
{
    ddlCustomer.Items.Insert(0, new ListItem("Choose a Customer", "0"));
}