Autocomplete textbox in ASP.NET

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C#

i want to use auto complete textbox using ajax with the multiple tables and the list of the autocomplete with the table name and search items.

What I have tried:

html code :

<asp:ScriptManager ID="ScriptManager1" runat="server"
EnablePageMethods = "true">

 
<asp:TextBox ID="txtContactsSearch" runat="server">
<cc1:AutoCompleteExtender ServiceMethod="SearchCustomers"
    MinimumPrefixLength="2"
    CompletionInterval="100" EnableCaching="false" CompletionSetCount="10"
    TargetControlID="txtContactsSearch"
    ID="AutoCompleteExtender1"  runat="server" FirstRowSelected = "false">

C# code :

public static List<string> SearchCustomers(string prefixText, int count)
{
    using (SqlConnection conn = new SqlConnection())
    {
        conn.ConnectionString = ConfigurationManager
                .ConnectionStrings["constr"].ConnectionString;
        using (SqlCommand cmd = new SqlCommand())
        {
            cmd.CommandText = "select ContactName from Customers where " +
            "ContactName like @SearchText + '%'";
            cmd.Parameters.AddWithValue("@SearchText", prefixText);
            cmd.Connection = conn;
            conn.Open();
            List<string> customers = new List<string>();
            using (SqlDataReader sdr = cmd.ExecuteReader())
            {
                while (sdr.Read())
                {
                    customers.Add(sdr["ContactName"].ToString());
                }
            }
            conn.Close();
            return customers;
        }
    }
}