三层架构：Helper层

三层架构：Helper层

  public int count(string sql)
       {
           SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=DB_class;User ID=sa;Pwd=123;");
           conn.Open();

           SqlCommand cmd = new SqlCommand(sql, conn);

           int num = (int)cmd.ExecuteScalar();
           conn.Close();
           return num;
           
       }
       public int count1(string sql)
       {
           SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=DB_class;User ID=sa;Pwd=123;");

           conn.Open();
           SqlCommand cmd = new SqlCommand(sql, conn);
           int i = cmd.ExecuteNonQuery();

           conn.Close();
           return i;

       }
       public DataTable count2(string sql)
       {

           SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=DB_class;User ID=sa;Pwd=123;");

           conn.Open();

           SqlCommand cmd = new SqlCommand(sql, conn);

           SqlDataAdapter dr = new SqlDataAdapter(cmd);

          
           DataSet ds = new DataSet();
           dr.Fill(ds, "shopping");

           DataTable dt = ds.Tables["shopping"];
          
           return dt;

       }