public DataTable GetAllInventory()

         {

             // Prep command object.

             string sql = "Select * From Inventory";

             SqlCommand cmd = new SqlCommand(sql, this.sqlCn);

             SqlDataReader dr = cmd.ExecuteReader();

             // This will hold the records.

             DataTable inv = new DataTable();

             // Fill the DataTable with data from the reader and clean up.

             //通过所提供的 IDataReader，用某个数据源的值填充 DataTable。 如果 DataTable 已经包含行，则从数据源传入的数据将与现有的行合并。

             inv.Load(dr);

             //也可以用dr循环获取数据并赋值给DataRow

             dr.Close();

             return inv;

         }

 DataTable dt = new DataTable();

             dt.Columns.Add("col1");

             dt.Columns.Add("col2");

             while (dr.Read())

             {

                 DataRow  row=new DataRow();

                 row["col1"] = dr["col1"];

                 row["col2"] = dr["col2"];

                 dt.Rows.Add(row);

             }

             dt.AcceptChanges();