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>();
}

Validation of viewstate MAC failed

Error:-

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

Answer:-
if u get this error just add attribute EnableViewStateMac="false" in page tag

Example:-<%@ Page Language="C#" EnableViewStateMac="false" >

Get lable control text in javascript

var x = document.getElementById('<%=LableId.ClientID %>').textContent;

this work in firefox also

Sql Server identity

identity
To change identity first drop identity column and then add new identity column like
this example

drop identity column

alter table tb_name
drop column col_name

add identity column

alter table tb_name
add columnname int identity(100,1)