LINQ 不支持指定的类型成员“DayOfWeek”

Question

我已经尝试使用this SO question 中的选项。我仍然收到以下错误：

The specified type member 'DayOfWeek' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

现在已编辑问题以包含我要实现的目标的完整代码。它基本上需要拉取一周中每天发送的平均短信数。

这是我的代码：

var weekDays = rad.SMSSentItems
    .Where(x => x.Status == "DELIVRD")
    .GroupBy(x => x.StatusDate.Value.DayOfWeek)
    .Select(g => new
    {
        DayOfWeek = g.Key,
        Count = g.Count()
    })
    .ToList();


int avgSMSPerMonday = 0;
int avgSMSPerTuesday = 0;
int avgSMSPerWednesday = 0;
int avgSMSPerThursday = 0;
int avgSMSPerFriday = 0;
int avgSMSPerSaturday = 0;
int avgSMSPerSunday = 0;
int totalSMSPerDay = 0;

foreach (var day in weekDays)
{
    totalSMSPerDay = rad.SMSSentItems.Where(x => (DbFunctions.TruncateTime(x.StatusDate).Value.DayOfWeek == day.DayOfWeek) && (x.Status == "DELIVRD")).ToList().Count;

    if (day.DayOfWeek == DayOfWeek.Monday)
        avgSMSPerMonday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Tuesday)
        avgSMSPerTuesday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Wednesday)
        avgSMSPerWednesday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Thursday)
        avgSMSPerThursday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Friday)
        avgSMSPerFriday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Saturday)
        avgSMSPerSaturday = totalSMSPerDay / day.Count;
    else if (day.DayOfWeek == DayOfWeek.Sunday)
        avgSMSPerSunday = totalSMSPerDay / day.Count;
}

使用 Camillo 的代码更新代码：

var weekDays = rad.SMSSentItems
                            .Where(x => x.Status == "DELIVRD")
                            .GroupBy(x => x.StatusDate.Value.DayOfWeek)
                            .Select(g => new
                            {
                                DayOfWeek = g.Key,
                                Count = g.Count()
                            })
                            .ToDictionary(x => x.DayOfWeek, x => x.Count);

                int mondayCount = 0;
                int tuesdayCount = 0;
                int wednessdayCount = 0;
                int thursdayCount = 0;
                int fridayCount = 0;
                int saturdayCount = 0;
                int sundayCount = 0;

                //determine average number of sms's sent per day of week
                foreach (var day in weekDays)
                {
                    int daysCount = rad.SMSSentItems
                        .Where(x => (x.StatusDate.Value.DayOfWeek == day.Key)
                                 && x.Status == "DELIVRD")
                        .Count();

                    if (day.Key == DayOfWeek.Monday)
                        mondayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Tuesday)
                        tuesdayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Wednesday)
                        wednessdayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Thursday)
                        thursdayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Friday)
                        fridayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Saturday)
                        saturdayCount = daysCount / day.Value;
                    else if (day.Key == DayOfWeek.Sunday)
                        sundayCount = daysCount / day.Value;
                }

我仍然留下从第一个查询中得到的初始错误，如下所示：

The specified type member 'DayOfWeek' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported

Answer 1

您不需要做所有这些检查，您可以使用 Dictionary<DayOfWeek, int> 代替：

var weekDays = rad.SMSSentItems
    .Where(x => x.Status == "DELIVRD")
    .GroupBy(x => x.StatusDate.Value.DayOfWeek)
    .Select(g => new
    {
        DayOfWeek = g.Key,
        Count = g.Count()
    })
    .ToDictionary(x => x.DayOfWeek);

int mondayCount = weekDays[DayOfWeek.Monday];
int tuesdayCount = weekDays[DayOfWeek.Tuesday];
//...

如果您不确定某一天是否有值，请改用TryGetValue：

weekDays.TryGetValue(DayOfWeek.Monday, out mondayCount);

如果你想要一周中某一天的平均值，你可以使用这样的东西：

foreach (var day in weekDays)
{
    int daysCount = rad.SMSSentItems
        .Where(x => x.StatusDate.Value.DayOfWeek == day.DayOfWeek
                 && x.Status == "DELIVRD")
        .Count();

    int dayAverage = day.Count / daysCount;
}