C# 常用工具方法之DataTable（一）

1、datatable 转 泛型t的list

        /// <summary>
        /// 数据集datatable转换成list集合
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="dttemp"></param>
        /// <returns></returns>
        public static list<t> tolistbydatatable<t>(datatable dttemp)
        {
            if (dttemp == null || dttemp.rows.count == 0)
            {
                return null;
            }
            list<t> lstresult = new list<t>();

            for (int j = 0, l = dttemp.rows.count; j < l; j++)
            {
                t _t = (t)activator.createinstance(typeof(t));
                propertyinfo[] propertys = _t.gettype().getproperties();
                foreach (propertyinfo pi in propertys)
                {
                    for (int i = 0, k = dttemp.columns.count; i < k; i++)
                    {
                        // 属性与字段名称一致的进行赋值    
                        if (pi.name.tolower().equals(dttemp.columns[i].columnname.tolower()))
                        {
                            if (dttemp.rows[j][i] != dbnull.value)
                            {
                                switch (pi.propertytype.tostring())
                                {
                                    case "system.int32":
                                        pi.setvalue(_t, nall.toint(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.int64":
                                        pi.setvalue(_t, nall.tolong(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.datetime":
                                        pi.setvalue(_t, nall.todatetime(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.string":
                                        pi.setvalue(_t, dttemp.rows[j][i].tostring(), null);
                                        break;
                                    case "system.boolean":
                                        pi.setvalue(_t, nall.toboolean(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.guid":
                                        pi.setvalue(_t, nall.toguid(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.single":
                                        pi.setvalue(_t, convert.tosingle(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.double":
                                        pi.setvalue(_t, convert.todouble(dttemp.rows[j][i].tostring()), null);
                                        break;
                                    case "system.object":
                                        pi.setvalue(_t, dttemp.rows[j][i], null);
                                        break;
                                }
                            }
                            else
                            {
                                switch (pi.propertytype.tostring())
                                {
                                    case "system.int32":
                                        pi.setvalue(_t, -1, null);
                                        break;
                                    case "system.int64":
                                        pi.setvalue(_t, -1, null);
                                        break;
                                    case "system.datetime":
                                        pi.setvalue(_t, new datetime(0x76c, 1, 1), null);
                                        break;
                                    case "system.boolean":
                                        pi.setvalue(_t, false, null);
                                        break;
                                    case "system.guid":
                                        pi.setvalue(_t, guid.empty, null);
                                        break;
                                    case "system.single":
                                        pi.setvalue(_t, 0.0f, null);
                                        break;
                                    case "system.double":
                                        pi.setvalue(_t, 0.0, null);
                                        break;
                                    case "system.string":
                                        pi.setvalue(_t, string.empty, null);
                                        break;
                                    default:
                                        pi.setvalue(_t, null, null);
                                        break;
                                }
                            }
                            break;
                        }
                    }
                }
                lstresult.add(_t);
            }
            return lstresult;
        }

2、datatable 转 hashtable

        /// <summary>
        /// datatable转hashtable
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="key"></param>
        /// <returns></returns>
        public static hashtable tohashtablebydatarow(datatable dt, int key)
        {
            hashtable ht = new hashtable();
            for (int i = 0; i < dt.columns.count; i++)
            {
                ht.add(dt.columns[i].columnname, dt.rows[key][i]);
            }
            return ht;
        }

3、datatable 转 hashtable

        /// <summary>
        ///  转换哈希表
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static list<hashtable> tohashtablebydatatable<t>(datatable dt)
        {
            list<hashtable> listht = new list<hashtable>();
            for (int i = 0; i < dt.rows.count; i++)
            {
                hashtable ht = new hashtable();
                ht.add(i, dt.rows[i]);
                listht.add(ht);
            }
            return listht;
        }

4、datatable 按照某列进行条件拆分

        /// <summary>
        /// 拆分dt，返回相同数据结构的多个dt
        /// [excel需要去掉第一行标题]
        /// </summary>
        /// <param name="dt">原始数据dt</param>
        /// <param name="condition">第几列数据，按照这一列进行拆分</param>
        /// <param name="orderstr">排序条件，dataview的排序条件</param>
        /// <returns></returns>
        public static list<datatable> splitdtsamestruct(datatable dt,int columnnum,string orderstr) {
            //定义返回对象
            list<datatable> listdt = new list<datatable>();
            //按照条件进行筛选
            list<string> conditionstr = new list<string>();
            foreach (datarow dr in dt.rows)
            {
                //筛选字段的值
                string key = dr["column"+ columnnum].tostring();
                //不存在新增进条件conditionstr中
                if (!isexit(conditionstr,key)) {
                    conditionstr.add(key);
                }
            }
            //根据条件conditionstr集合进行拆分dt
            //1、将dt数据源按照字段排序
            dt.columns.add();
            dataview view = new dataview(dt);
            //正序排列
            view.sort = orderstr;//"column"+ columnnum + " asc";
            dt = view.totable();
            foreach (string str in conditionstr)
            {
                //按照条件进行抽取数据
                datarow[] dr = dt.select("column"+ columnnum + "='"+str+"'");
                //抽出的数据存入临时的tempdt中
                datatable tempdt = new datatable();
                tempdt = dt.clone();//拷贝框架
                for (int i = 0; i < dr.length; i++)
                {
                    tempdt.importrow((datarow)dr[i]);
                }
                //tempdt存入返回对象listdt中
                listdt.add(tempdt);
            }
            return listdt;
        }

日常工作常遇到的utils中积累的代码，可以优化的地方希望多多指教！