C#datatable不能正确显示平均数

Question

AVG不能正常显示平均数，怎么办

 DataTable dt = new DataTable("rawData");

            //新建行和列
            dt.Columns.Add("Time");
            dt.Columns.Add("FeederErr");
            dt.Columns.Add("NozzleErr");
            dt.Columns.Add("HeadErr");
            dt.Columns.Add("AVG");

            //获取数据
            DataTable a = BLL.NXTChartMgr.GetNozzleData();
            DataTable b = BLL.NXTChartMgr.GetFeederData();
            DataTable c = BLL.NXTChartMgr.GetHeadData();

            //先循环A,循环一条A，再找B和C，再插入到结果表里
            foreach (DataRow drA in a.Rows)
            {
                //得到B和C的Err
                DataRow drB = b.Select("MACHINE='" + drA["MACHINE"] + "' and uplddte= '" + drA["uplddte"] +"'")[0];
                DataRow drC = c.Select("MACHINE='" + drA["MACHINE"] + "' and uplddte= '" + drA["uplddte"] +"'")[0];
                //计算avg值
                List<double> list = new List<double>();
                for (int i = 0; i < a.Rows.Count; i++)
                {
                    double d = (Convert.ToDouble(a.Rows[i]["NozzleErr"]) + Convert.ToDouble(b.Rows[i]["FeederErr"]) + Convert.ToDouble(c.Rows[i]["HeadErr"])) / 3;
                    list.Add(d);
                }

                //新建一行
                DataRow dr = dt.NewRow();
                //赋值
                dr["Time"] = drA["uplddte"];
                dr["NozzleErr"] = drA["NozzleErr"];
                dr["FeederErr"] = drB["FeederErr"];
                dr["HeadErr"] = drC["HeadErr"];
                dr["AVG"] = list;
                //构造dr后，插入dt
                dt.Rows.Add(dr);
            }

            return dt;

Answer 1

datatable不能显示list泛型或者列表的，你可以把list转换成string的形式。
如：
string strAvg ="";
foreach(double avg in list)
{
strAvg += avg + ",";
}
strAvg = strAvg.substring(0, strAvg.length-1);

dr["AVG"] = strAvg；