1、json串如下所示

2、str是json串,然后分层去找串中所需的数据(hisVal数据),转化成dictionary
var str = HandlePIData.GetDataPI(fromtime, totime, "ZBWD"); //此语句获取的数据如上图所示,是用户自己编写的方法。
var dict = JsonConvert.DeserializeObject<Dictionary<object, object>>(str);
var data = JsonConvert.DeserializeObject<Dictionary<object, object>>(dict["data"].ToString());
var hisval = JsonConvert.DeserializeObject<Dictionary<object, double>>(data["hisVal"].ToString());
3、用minval.Value读取最小值数值
var minval = hisval.Aggregate((x, y) => x.Value > y.Value ? y : x);//取最小值
var maxval = hisval.Aggregate((x, y) => x.Value > y.Value ? x : y);//取最大值
dt_CC.Rows.Add("5904", "TUND_LOW_TEMP", "CC",maxval.Value- minval.Value, "");//使用最大值,最小值