C# 在datatable中添加自定义字段

 DataTable dt = new DataTable();
 sql.Append("    SELECT  a from b ")；
  dt = SqlHelper.GetDataTable(sql.ToString());

  sql = new StringBuilder();
  sql.Append("  SELECT c from d ");
 var jcdt = SqlHelper.GetDataTable(sql.ToString());

//重要
  DataColumn dataColumn1 = new DataColumn("自定义字段名称", typeof(Int32));
                DataColumn dataColumn2 = new DataColumn("自定义字段名称", typeof(Int32));
  dt.Columns.Add(dataColumn1);
                dt.Columns.Add(dataColumn2);
//给新增的字段赋值
  foreach (DataRow item in dt.Rows)//item：行  相当于dr
                {
                    DataRow[] num = jcdt.Select("ID=" + item[0]);//根据某个字段查询的数据  item：行　【0】：列
                    item[5] = num.Count();
                    int i = num.Count();
                    DataRow[] hg = jcdt.Select("ID=" + item[0] + "and VerID=1");
                    item[6] = hg.Count();
                    item[7] = num.Count() - hg.Count();
                    item[8] = num.Count() > 0 ? (Convert.ToDecimal(hg.Count()) / Convert.ToDecimal(num.Count()) * 100).ToString("f2") + "%" : "0.00%";
                }

 return format.ResultJsonData("SUCCESS", "获取信息成功！", dt);