Linq 操作DataTable

Posted 2020-10-26 木头南方

class ClientStruct  
        {  
            public string ID = "ID";  
            public string Name = "Name";  
            public string Company = "Company";  
            public string CreatedDate = "CreatedDate";  
        }  

public string[,] infoArr = new string[,] { { "1", "百度", "baidu", "201303" }, { "2", "迅雷", "xunlei", "201302" }, { "3", "谷歌", "guge", "201301" } }; 

protected void LinqDataTable()  
        {  
            DataRow row;  
            ClientStruct cs = new ClientStruct();  
            DataTable dtTable = new DataTable();  
            dtTable.Columns.Add(cs.ID);  
            dtTable.Columns.Add(cs.Name);  
            dtTable.Columns.Add(cs.Company);  
            dtTable.Columns.Add(cs.CreatedDate);  
            for (int i = 0; i < 3; i++)  
            {  
                row = dtTable.NewRow();  
                row[cs.ID] = infoArr[i, 0];  
                row[cs.Name] = infoArr[i, 1];  
                row[cs.Company] = infoArr[i, 2];  
                row[cs.CreatedDate] = infoArr[i, 3];  
                dtTable.Rows.Add(row);  
            }  
  
            //遍历DataTable，取出所有的ID  
            List<string> lstID = (from d in dtTable.AsEnumerable()  
                                  select d.Field<string>(cs.ID)).ToList<string>();  
  
            //遍历DataTable，将其中的数据对应到ClientStruct中：  
            List<ClientStruct> list = (from x in dtTable.AsEnumerable()  
                                       orderby x.Field<string>(cs.Company)  
                                       select new ClientStruct  
                                       {  
                                           ID = x.Field<string>(cs.ID),  
                                           Name = x.Field<string>(cs.Name),  
                                           Company = x.Field<string>(cs.Company),  
                                           CreatedDate = x.Field<string>(cs.CreatedDate)  
                                       }).ToList<ClientStruct>();  
  
            //遍历DataTable，并将上面的List结果存储到Dictionary中：  
            Dictionary<string, ClientStruct> dic = list.ToDictionary(p => p.Company);  
            //p作为string键值来存储  
        }  

其实关键是AsEnumerable()方法，返回一个 System.Collections.Generic.IEnumerable<T> 对象

 

误区：

一：

 var dd=from DataRow r in dt.Rows select r ;
            foreach (var item in dd)
            {
                var hh = item;
            }

二：

  var dtrows = dt.Rows.Cast<DataRow>();
            var aaaaaa = dtrows.ToList();

本来认为通过以上两种方式可以方便的得到 列以及对应的值  方便序列化成json

调试：

结果并非想象的   列名 对应相应的值  其中ItemArray中只是对应的值  没中对应的列名 

  Table是原始的得到的DataTable数据   即使通过linq进行过滤  也没用  里面仍然是原始数据

dd.Skip(pagination.rows * (pagination.page - 1)).Take(pagination.rows);

所以不要想着通过这种方式来 对DataTable进行分页  然后序列换json 在前台通过Grid进行显示，因为序列化的结果并不是   列名：值 的json数据。

 

 

实战：

  public string GetListJson(Pagination pagination, string keyword, string F_EtId,
            string F_CreatorTime_Start, string F_CreatorTime_End, string F_CreatorUserId)
        {

            string sql = string.Format(@"
                   WITH AA AS(
                        SELECT rec.F_ResUnit,rec.F_ResUnitID,
                        COUNT(0) AS zongliang,
                        SUM(CASE  WHEN item.F_EvalState<>\'4\' THEN 1 ELSE 0 END) AS weizhenggai,
                        SUM(CASE  WHEN item.F_EvalState=\'4\' THEN 1 ELSE 0 END) AS yichuli,
                        SUM(CAST(item.F_DedScore AS DECIMAL(18,1))) AS koufeizhi
                        FROM dbo.T_EvalReportItem item 
                        INNER JOIN dbo.T_EvalDutyRec rec
                        ON rec.F_ERIFId=item.F_Id
                        INNER JOIN dbo.T_EvalReport report 
                        ON report.f_id=item.F_ERId AND report.F_EvalType=\'1\'--派单类
                        GROUP BY rec.F_ResUnit,F_ResUnitID
                    )
                    SELECT unit.F_Code,unit.F_ResUnit,unit.F_UnitType, 
                    CASE WHEN AA.zongliang IS NULL THEN 0 ELSE AA.zongliang END zongliang,
                    CASE WHEN AA.yichuli IS NULL THEN 0 ELSE AA.yichuli END yichuli,
                    CASE WHEN AA.weizhenggai IS NULL THEN 0 ELSE AA.weizhenggai END weizhenggai,
                    CASE WHEN AA.koufeizhi IS NULL THEN 0 ELSE AA.koufeizhi END koufeizhi,
                    CASE WHEN AA.zongliang IS NULL THEN 0 ELSE CAST((CAST(yichuli AS DECIMAL(18,2))/zongliang) AS DECIMAL(18,4)) END baifeibi
                     --百分比
                    FROM T_ResponsibilityUnit unit 
                    LEFT JOIN AA  
                    ON AA.F_ResUnitID = unit.F_Code
                                           ");
            DataTable dt = new DataTable();
            dt = DbHelper.GetTable(sql);
            var data =
                from item in dt.AsEnumerable().Skip(pagination.rows*(pagination.page - 1)).Take(pagination.rows)
                select new
                {
                    F_Code = item.Field<string>("F_Code"),
                    F_ResUnit = item.Field<string>("F_ResUnit"),
                    F_UnitType = item.Field<string>("F_UnitType"),
                    zongliang = item.Field<int>("zongliang"),
                    yichuli = item.Field<int>("yichuli"),
                    weizhenggai = item.Field<int>("weizhenggai"),
                    koufeizhi = item.Field<object>("koufeizhi"),
                    baifeibi = item.Field<object>("baifeibi")
                };
            pagination.records = dt.Rows.Count;
            var dataList = new
            {
                rows = data.ToList(),
                total = pagination.total,
                page = pagination.page,
                records = pagination.records
            };
            //IEnumerable<IGrouping<string, DataRow>> result = dt.Rows.Cast<DataRow>().GroupBy<DataRow, string>(dr => dr["A"].ToString());//按A分组
            return dataList.ToJson();
        }

 

 

 

转自:http://blog.csdn.net/joyhen/article/details/8717552