用.NET语言写出计算股票技术指标KDJ，返回值为datatable类型，double类型全部四舍五入保留3位小数。

以下是用.NET语言写出计算股票技术指标KDJ的代码，返回值为datatable类型，double类型全部四舍五入保留3位小数：

using System;
using System.Data;

namespace KDJ
{
    public class KDJCalculator
    {
        public static DataTable CalculateKDJ(DataTable dataTable, int n, int m1, int m2)
        {
            DataTable resultTable = new DataTable();
            resultTable.Columns.Add("K", typeof(double));
            resultTable.Columns.Add("D", typeof(double));
            resultTable.Columns.Add("J", typeof(double));

            double[] high = new double[dataTable.Rows.Count];
            double[] low = new double[dataTable.Rows.Count];
            double[] close = new double[dataTable.Rows.Count];
            double[] rsv = new double[dataTable.Rows.Count];
            double[] k = new double[dataTable.Rows.Count];
            double[] d = new double[dataTable.Rows.Count];
            double[] j = new double[dataTable.Rows.Count];

            for (int i = 0; i < dataTable.Rows.Count; i++)
            {
                high[i] = Convert.ToDouble(dataTable.Rows[i]["High"]);
                low[i] = Convert.ToDouble(dataTable.Rows[i]["Low"]);
                close[i] = Convert.ToDouble(dataTable.Rows[i]["Close"]);

                if (i < n - 1)
                {
                    rsv[i] = 0;
                    k[i] = 0;
                    d[i] = 0;
                    j[i] = 0;
                }
                else
                {
                    double maxHigh = double.MinValue;
                    double minLow = double.MaxValue;

                    for (int j = i - n + 1; j <= i; j++)
                    {
                        if (high[j] > maxHigh)
                        {
                            maxHigh = high[j];
                        }

                        if (low[j] < minLow)
                        {
                            minLow = low[j];
                        }
                    }

                    rsv[i] = (close[i] - minLow) / (maxHigh - minLow) * 100;

                    if (i == n - 1)
                    {
                        k[i] = rsv[i];
                        d[i] = k[i];
                    }
                    else
                    {
                        k[i] = (m1 - 1) * d[i - 1] / m1 + rsv[i] / m1;
                        d[i] = (m2 - 1) * d[i - 1] / m2 + k[i] / m2;
                    }

                    j[i] = 3 * k[i] - 2 * d[i];
                }

                DataRow row = resultTable.NewRow();
                row["K"] = Math.Round(k[i], 3);
                row["D"] = Math.Round(d[i], 3);
                row["J"] = Math.Round(j[i], 3);
                resultTable.Rows.Add(row);
            }

            return resultTable;
        }
    }
}

其中，n为KDJ指标的周期，m1为平滑因子1，m2为平滑因子2。使用时，可以将股票数据存储在一个DataTable中，然后调用CalculateKDJ方法进行计算，返回一个包含KDJ指标的DataTable。