C# 查找Min DateTime并将DateTime分配给局部变量

我试图得到最小日期时间，然后是最大日期时间，并比较两者。但是，当我试图从LINQ中提取DateTime值时，会出现以下错误。任何帮助都将不胜感激

在此行引发错误：appChartDateStart=Convert.ToDateTime（dateStartType）

艾伦

无法将类型为“WhereSelectEnumerableTerator

2[System.Linq.iGroup

2[System.DateTime，LatencyApp.Domain.Models.ChartHist]，f_uAnonymousType2`1[System.DateTime]]的对象强制转换为类型“System.IConvertible”

我的代码：

        DateTime appChartDateStart = DateTime.MinValue;
        DateTime appChartDateEnd = DateTime.MinValue;
        var dateStartType = from row in myRow
                                group row by row.LoginDateTime_Rounded into g
                                select new { MinDateTime = g.Min(row => row.LoginDateTime_Rounded) };
        var dateEndType = from row in myRow
                                group row by row.LoginDateTime_Rounded into g
                                select new { MinDateTime = g.Max(row => row.LoginDateTime_Rounded) };
        appChartDateStart = Convert.ToDateTime(dateStartType);
        appChartDateEnd = Convert.ToDateTime(dateEndType);
        TimeSpan difAppChart = appChartDateEnd - appChartDateStart;

---

这是因为您的select正在创建一个具有MinDateTime属性的匿名类型。Convert.TomDateTime方法不知道如何转换此匿名类型。试着做：

DateTime appChartDateStart = DateTime.MinValue;
DateTime appChartDateEnd = DateTime.MinValue;
var dateStartType = (from row in myRow
                        group row by row.LoginDateTime_Rounded into g
                        select new { MinDateTime = g.Min(row => row.LoginDateTime_Rounded) }).FirstOrDefault();
var dateEndType = (from row in myRow
                        group row by row.LoginDateTime_Rounded into g
                        select new { MinDateTime = g.Max(row => row.LoginDateTime_Rounded) }).FirstOrDefault();
appChartDateStart = Convert.ToDateTime(dateStartType);
appChartDateEnd = Convert.ToDateTime(dateEndType);
TimeSpan difAppChart = appChartDateEnd - appChartDateStart;

---

我在LINQ sintax上做的，效果很好，也比较干净：

DateTime appChartDateStart = DateTime.MinValue;
DateTime appChartDateEnd = DateTime.MinValue;

var dateStartType = myRow.GroupBy(x => x.LoginDateTime_Rounded).Select(x => x.Key).Min();
var dateEndType = myRow.GroupBy(x => x.LoginDateTime_Rounded).Select(x => x.Key).Max();

TimeSpan difAppChart = appChartDateEnd - appChartDateStart;

完成代码：

        DateTime appChartDateStart = DateTime.MinValue;
        DateTime appChartDateEnd = DateTime.MinValue;
        if (histByApp.Count() != 0)
        {
            var dateStartType = histByApp.GroupBy(x => x.LoginDateTime_Rounded).Select(x => x.Key).Min();
            var dateEndType = histByApp.GroupBy(x => x.LoginDateTime_Rounded).Select(x => x.Key).Max();
            appChartDateStart = Convert.ToDateTime(dateStartType);
            appChartDateEnd = Convert.ToDateTime(dateEndType);
        }
        TimeSpan difAppChart = appChartDateEnd - appChartDateStart;

---

谢谢你的回复。对，我忘了这是一个集合和单个对象。试试我修改过的代码。编辑你的答案，并将其包含在最后。