string uname = "XX";
string pwd = "ZZ";
using(SqlConnection comn = new SqlConnection("Data Source=.;Initial Catalog=userinformation;Integrated Security=True"))
{
   comn.Open();
   SqlCommand command1 = new SqlCommand("select * from userinformation where username='"+uname+"'", comn);
   SqlDataReader reader1 = command1.ExecuteReader();
   if(reader1.Read())
   {
      if(reader1["password"].Equals(pwd))
      {
          Response.Write("<script>alert('登录验证正确！');</script>");
      }
      else
      {
         Response.Write("<script>alert('密码错误！');</script>");
      }
   }
   else
   {
      Response.Write("<script>alert('用户名错误！');</script>");
   }
}