autocomplete extender doesnt show the values in textbox

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ASP.NET

Hi
I am using autocomplete extender in my application.the control doesnt giving the values in textbox.And i am using webservice to get the values.

this my web method code and design code

[WebMethod]
    public List<string> GetNames(string prefixText)
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ToString());
        con.Open();
        SqlCommand cmd = new SqlCommand("select * from familytwo where Name like @Name+'%'", con);
        cmd.Parameters.AddWithValue("@Name", prefixText);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        List<string> Names = new List<string>();
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            Names.Add(dt.Rows[i][1].ToString());
        }
        return Names;
    }

html code:

<asp:TextBox ID="TextBox2"  runat="server" Width="244px">
                     <ajax:AutoCompleteExtender ID="AutoCompleteExtender"  runat="server" TargetControlID="TextBox2" ServiceMethod="GetNames"
                     ServicePath="~/autocompleteasmx.asmx" MinimumPrefixLength="1" EnableCaching="true" CompletionInterval="1000" CompletionSetCount="1">

whats the issue in that..
can anyone help me to solve this?