Auto Complete Control in .Net

Write Code in .aspx Page
<asp:TextBox ID="txtbox1" runat="server"></asp:TextBox>

    <cc1:AutoCompleteExtender

      Enabled="true"

       UseContextKey ="true"

        MinimumPrefixLength ="1"

         ServiceMethod ="getdata"

           CompletionInterval="10"

        TargetControlID ="txtbox1"

     ID="AutoCompleteExtender2" runat="server">

    </cc1:AutoCompleteExtender>

Write a Method in .aspx.cs
using System.Collections.Generic;


[System.Web.Services.WebMethodAttribute(), System.Web.Script.Services.ScriptMethodAttribute()]
public static string[] Getdata(string prefixText, int count,string contextKey)
{

List <string> response = new List <string>();

for (int i = 0; i =10; i++)
{
response.Add(prefixText+i);

}
return response.ToArray<string>();
}