//写一个SQLHelper


public class SQLhelper
   {
      public static readonly string connstr =ConfiguationManager.ConnectionStrings["connstr"].ConnectionString;
      
      public static int ExcuteNonQuery(string sql ,params SqlParameter [] parameters )
         {
             using(SqlConnection conn=new SqlConnection(connstr))
               {
                     conn.open();
                     using(SqlCommand cmd=conn.createCommand())
                       {
                          cmd.CommandText=sql;
                          cmd.Parameter.AddRange(parameters);
                          return cmd.ExcuteNonQuery();
                        }
                }

          }
       public static int ExcuteScalar(string sql ,params SqlParameter [] parameters )
         {
             using(SqlConnection conn=new SqlConnection(connstr))
               {
                     conn.open();
                     using(SqlCommand cmd=conn.createCommand())
                       {
                          cmd.CommandText=sql;
                          cmd.Parameter.AddRange(parameters);
                          return cmd.ExcuteScalar();
                        }
                }

          }
       public static DataTable DataTable(string sql ,params SqlParameter [] parameters )
         {
             
            using(SqlConnection conn=new SqlConnection(connstr))
               {
                     conn.open();
                     using(SqlCommand cmd=conn.createCommand())
                       {
                          cmd.CommandText=sql;
                          cmd.Parameter.AddRange(parameters);
                            using(SqlDataAdapter da=new SqlDataAdapter(cmd))
                               {
                                 DataTable dt = new DataTable();
                                 da.Fill(dt);
                                 return dt;
                                }

                        }
                }


          }

    }