//identify login
protected void btnLogin_Click(object sender, EventArgs e)
{
lt.Add(txtUserName);
lt.Add(txtPassword);
if (CustomerDB.CheckLogin(lt))
{
Session["user"] = lt[0].Text;
Response.Redirect("~/Manage.aspx");//if login successfully, go to Manage page
}
else
{
lblError.Text = "Invalid user or password";//display error message,if not login properly
}
}