Coolite 

    <ext:Store ID="strNames" runat="server" OnRefreshData="strNames_RefreshData">
        <Reader>
            <ext:JsonReader>
                <Fields>
                    <ext:RecordField Name="NameId" />
                    <ext:RecordField Name="FullName" />
                </Fields>
            </ext:JsonReader>
        <Reader>
    </ext:StoreID>

    <ext:ComboBox ID="cbNames" runat="server" StoreID="strNames" DisplayField="FullName" ValueField="NameId" HideTrigger="true" MinChars="1" />

protected void strNames_RefreshData(object sender, StoreRefreshDataEventArgs e)
{
    // This function should take the text already typed and search for any records beginning
    // with the values typed. Name Search is looking in the database is:
    // SELECT TOP 10 * FROM Names WHERE FullName LIKE search + '%'

    string search = ((ListItem)cbNames.Value).Value;
    DataTable names = null;

    if (!string.IsNullOrEmpty(search))
    {
        // Make database connection here, return results as DataTable
        names = namesDb.NameSearch(search);
    }

    strNames.DataSource = names;
    strNames.DataBind();
}

<Proxy>
    <ext:DataSourceProxy />
</Proxy>