void Page_Load(Object sender, EventArgs e)
{
  String Q;
  Sql command cmd;
  Sql DataReader dr;


  SqlConnection conn = new SqlConnection(); 

  conn.ConnectionString = ConfigurationManager.ConnectionStrings        ["cn"].ConnectionString.ToString(); 

 conn.Open(); 
          
 Q = "select * from tablename";
               
cmd= New Sqlcommand(Q, conn);  
          
dr = cmd.ExecuteReader();          
          
Gridview1.DataSource = dr;
            
Gridview1.DataBind();
}