关于dt分组、计数、排序的实例

 #region table去重复求和
                    var query = dt.Rows.Cast<DataRow>()
                        .OrderByDescending(n => n["OPERATION_TIME"])
                      .GroupBy(
                     s => new
                     {
                         MATERIAL_CODE = Convert.ToString(s["MATERIAL_CODE"]),
                         MATERIAL_NAME = Convert.ToString(s["MATERIAL_NAME"]),
                         STORAGE_STYLE = Convert.ToString(s["STORAGE_STYLE"]),
                         STORAGE_SIGN = Convert.ToString(s["STORAGE_SIGN"])
                     })
                     .Select(group => new
                     {
                         group.Key.MATERIAL_CODE,
                         group.Key.MATERIAL_NAME,
                         group.Key.STORAGE_STYLE,
                         group.Key.STORAGE_SIGN,
                         REMARK = group.First().Field<string>("REMARK"),
                         OPERATION_TIME = group.First().Field<string>("OPERATION_TIME"),
                         STORAGE_NUM = group.Sum(x => Convert.ToInt32(x["STORAGE_NUM"]))
                     });

                    if (query.ToList().Count > 0)
                    {
                        dtNew = dt.Clone();
                        query.ToList().ForEach(q =>
                        {
                            DataRow drNew = dtNew.NewRow();
                            drNew["MATERIAL_CODE"] = q.MATERIAL_CODE;
                            drNew["MATERIAL_NAME"] = q.MATERIAL_NAME;
                            drNew["REMARK"] = q.REMARK;
                            drNew["STORAGE_NUM"] = q.STORAGE_NUM;
                            drNew["STORAGE_STYLE"] = q.STORAGE_STYLE;
                            drNew["OPERATION_TIME"] = q.OPERATION_TIME;
                            drNew["STORAGE_SIGN"] = q.STORAGE_SIGN;
                            dtNew.Rows.Add(drNew);
                        });
                    }
                    #endregion