AjaxControlToolkit AutoCompleteExtender … how to fill from linq query?

<asp:TextBox ID="TagNameTextBox" runat="server"></asp:TextBox>

<ajaxToolkit:AutoCompleteExtender ID="TagNameTextBox_AutoCompleteExtender"
runat="server"   
ServiceMethod="GetTagNames"
 MinimumPrefixLength="2"
 EnableCaching="false"
DelimiterCharacters=""
Enabled="True"
TargetControlID="TagNameTextBox">
</ajaxToolkit:AutoCompleteExtender>


[System.Web.Services.WebMethod]
public static string[] GetTagNames(string prefixText, int count)
{
    mydatabase db = new mydatabase();
    return db.TagTables.Where(n => n.TagName.StartsWith(prefixText)).OrderBy(n => n.TagName).Select(n => n.TagName).Distinct().Take(count).ToArray();
}