怎么根据某个条件统计datatable表里的某一个字段的累加总和？最好说明白一点，谢谢，在线等 ..

Question

首先呢，是从一个文本文件里获取数据，然后存到datatable表里，记住数据库里面是没有的哦，因为今天的数据是不能加到数据库里的，所以只能读取到内存里，然后直接就在内存里进行统计的，有没有解决的方法....
我已经想了Ｎ天了，找了Ｎ天的答案了......
现在都没辙了.....
谢谢各位的帮助了....
我的分数不多了，希望各位不要嫌弃我分数给的太少，谢谢了.

Answer 1

用DataTable的Compute 方法啊。 
比如 定义了一个 Datatable table,
有 Total，id 字段。
下面的代码将id=5的全部累加起来。object sumObject;
sumObject = table.Compute("Sum(Total)", "ID = 5");

Answer 2

int sum = 0;
foreach(DataRow dr in dt.Rows)
{
    sum += int.Prase(dr["累加字段"].ToString());
}

Answer 3

貌似你说的太笼统了，能给具体的数据吗foreach或者for循环就够了

Answer 4

http://msdn.microsoft.com/en-us/library/system.data.datatable.compute.aspx

Answer 5

id  cItem  nMoney  nCount
1    训练　　100　　　　1
２　新手手册　300　　　　2
３　训练　　　500　　　　2
４　训练　　　120　　　　1
要根据cItem来统计nMoney和nCount的累加和
结果：训练的nMoney＝720,nCount=4
     新手手册的nMoney=300,nCount=2

Answer 6

就用Compute就可以，而且在程序里处理的代码也写出来了

Answer 7

 /*
            id  cItem  nMoney  nCount 
1    训练　　100　　　　1 
２　新手手册　300　　　　2 
３　训练　　　500　　　　2 
４　训练　　　120　　　　1 
    要根据cItem来统计nMoney和nCount的累加和 
   结果：训练的nMoney＝720,nCount=4 
         新手手册的nMoney=300,nCount=2
            */
            //定义表结构
            DataTable table = new DataTable();
            DataColumn c1 = new DataColumn("id");
            DataColumn c2 = new DataColumn("cItem", System.Type.GetType("System.String"));
            DataColumn c3 = new DataColumn("nMoney", System.Type.GetType("System.Int32"));
            DataColumn c4 = new DataColumn("nCount", System.Type.GetType("System.Int32"));
            //添加列
            table.Columns.Add(c1);
            table.Columns.Add(c2);
            table.Columns.Add(c3);
            table.Columns.Add(c4);
            //构造行
            DataRow r1 = table.NewRow();
            r1[0] = "1";
            r1[1] = "训练";
            r1[2] = "100";
            r1[3] = "1";
            //构造行
            DataRow r2 = table.NewRow();
            r2[0] = "2";
            r2[1] = "新手手册";
            r2[2] = "300";
            r2[3] = "2";
            //构造行
            DataRow r3 = table.NewRow();
            r3[0] = "3";
            r3[1] = "训练";
            r3[2] = "500";
            r3[3] = "2";
            //构造行
            DataRow r4 = table.NewRow();
            r4[0] = "4";
            r4[1] = "训练";
            r4[2] = "120";
            r4[3] = "1";            //添加行
            table.Rows.Add(r1);
            table.Rows.Add(r2);
            table.Rows.Add(r3);
            table.Rows.Add(r4);
            //计算
            //训练的nMoney＝720,nCount=4 
            int nMoney1 = Convert.ToInt32(table.Compute("sum(nMoney)", "cItem='训练'"));
            int nCount1 = Convert.ToInt32(table.Compute("sum(nCount)", "cItem='训练'"));            //新手手册的nMoney＝720,nCount=4 
            int nMoney2 = Convert.ToInt32(table.Compute("sum(nMoney)", "cItem='新手手册'"));
            int nCount2 = Convert.ToInt32(table.Compute("sum(nCount)", "cItem='新手手册'"));
            

Answer 8

关键是还是有点不懂啊，sum是复合函数，用时老提示异常问题.....老实例给个参考下...谢谢..

Answer 9

无效的聚合函数 Sum()和类型 String 的用法。 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.Data.DataException: 无效的聚合函数 Sum()和类型 String 的用法。源错误: 
行 80:                 //moneyObject = dt01.Compute("sum(nMoney)", "cItem='"+drItem["cItem"]+"'");
行 81:                 //countObject = dt01.Compute("sum(nCount)", "cItem='" + drItem["cItem"] + "'");
行 82:                 moneyObject = Convert.ToDouble(dt01.Compute("sum(nMoney)", "cItem='训练'"));
行 83:                 countObject = Convert.ToInt32(dt01.Compute("sum(nCount)","cItem='训练'"));
行 84:             }
 

Answer 10

用sum时会出现这个错误....不知道是为什么？

Answer 11

DataTable dt01 = new DataTable();
            dt01.Columns.Add("id");
            dt01.Columns.Add("cItem");
            dt01.Columns.Add("nMoney");
            dt01.Columns.Add("nCount");
            dt01.Columns.Add("dDateTime");            DataRow dr = dt01.NewRow();//1
            dr["id"] = "1";
            dr["cItem"] = "新手训练";
            dr["nMoney"] = "100";
            dr["nCount"] = "1";
            dr["dDateTime"] = "2009-11-02";            DataRow dr02 = dt01.NewRow();//2
            dr02["id"] = "2";
            dr02["cItem"] = "训练";
            dr02["nMoney"] = "300";
            dr02["nCount"] = "2";
            dr02["dDateTime"] = "2009-11-02";            DataRow dr03 = dt01.NewRow();//3
            dr03["id"] = "3";
            dr03["cItem"] = "训练";
            dr03["nMoney"] = "500";
            dr03["nCount"] = "8";
            dr03["dDateTime"] = "2009-11-02";            DataRow dr04 = dt01.NewRow();//4
            dr04["id"] = "4";
            dr04["cItem"] = "训练";
            dr04["nMoney"] = "600";
            dr04["nCount"] = "2";
            dr04["dDateTime"] = "2009-11-02";            DataRow dr05 = dt01.NewRow();//5
            dr05["id"] = "5";
            dr05["cItem"] = "升级手册";
            dr05["nMoney"] = "120";
            dr05["nCount"] = "1";
            dr05["dDateTime"] = "2009-01-02";            dt01.Rows.Add(dr);
            dt01.Rows.Add(dr02);
            dt01.Rows.Add(dr03);
            dt01.Rows.Add(dr04);
            dt01.Rows.Add(dr05);          
            //统计字段
            foreach (DataRow drItem in tableview.Rows)
            {
                double moneyObject;
                int countObject;
                //moneyObject = dt01.Compute("sum(nMoney)", "cItem='"+drItem["cItem"]+"'");
                //countObject = dt01.Compute("sum(nCount)", "cItem='" + drItem["cItem"] + "'");
                moneyObject = Convert.ToDouble(dt01.Compute("sum(nMoney)", "cItem='训练'"));
                countObject = Convert.ToInt32(dt01.Compute("sum(nCount)","cItem='训练'"));
            }

Answer 12

nMoney的类型要设置为int32,
 //moneyObject = dt01.Compute("sum(nMoney)", "cItem='"+drItem["cItem"].ToStrin()+"'"); 看看,

Answer 13

 dt01.Columns.Add("cItem", System.Type.GetType("System.String"));
            dt01.Columns.Add("nMoney", System.Type.GetType("System.Int32"));
            dt01.Columns.Add("nCount", System.Type.GetType("System.Int32"));
//moneyObject = dt01.Compute("sum(nMoney)", "cItem='"+drItem["cItem"].ToString()+"'");看看,
     

Answer 14

            //定义表结构
            DataTable table = new DataTable();
            DataColumn c1 = new DataColumn("id");
            DataColumn c2 = new DataColumn("cItem", System.Type.GetType("System.String"));
            DataColumn c3 = new DataColumn("nMoney", System.Type.GetType("System.Int32"));
            DataColumn c4 = new DataColumn("nCount", System.Type.GetType("System.Int32"));
            //添加列
            table.Columns.Add(c1);
            table.Columns.Add(c2);
            table.Columns.Add(c3);
            table.Columns.Add(c4);
            //构造行
            DataRow r1 = table.NewRow();
            r1[0] = "1";
            r1[1] = "训练";
            r1[2] = "100";
            r1[3] = "1";
            //构造行
            DataRow r2 = table.NewRow();
            r2[0] = "2";
            r2[1] = "新手手册";
            r2[2] = "300";
            r2[3] = "2";
            //构造行
            DataRow r3 = table.NewRow();
            r3[0] = "3";
            r3[1] = "训练";
            r3[2] = "500";
            r3[3] = "2";
            //构造行
            DataRow r4 = table.NewRow();
            r4[0] = "4";
            r4[1] = "训练";
            r4[2] = "120";
            r4[3] = "1";            //添加行
            table.Rows.Add(r1);
            table.Rows.Add(r2);
            table.Rows.Add(r3);
            table.Rows.Add(r4);            var test = table.AsEnumerable();
            var query =
                from p in test
                group p by p.Field<string>("cItem") into g
                select new { item = g.Key, students = g };            foreach (var g in query)
            {
                Console.WriteLine("{0}的nMoney＝{1},nCount={2} ", g.item, 
                    g.students.Sum(w => w.Field<int>("nMoney")), 
                    g.students.Sum(w => w.Field<int>("nCount")));
            }