不包括周末的列值的LINQ總和-有解無憂

我試圖計算一周中的作業時間與周末作業的時間不同。這就是我希望實作它的方式：

private void SetTotalCharge()
        {
            int.TryParse(MDate.ToString("MM"), out int month);
            int.TryParse(MDate.ToString("yyyy"), out int year);

            TotalCharge = 
               Decimal.Round(Convert.ToDecimal(db.MyTable
               .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & (a.Date.DayOfWeek != DayOfWeek.Saturday && a.Date.DayOfWeek != DayOfWeek.Sunday))
               .Select(a => a.RepairHours).Sum() * RateWeek
                 db.MyTable
               .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & (a.Date.DayOfWeek == DayOfWeek.Saturday && a.Date.DayOfWeek == DayOfWeek.Sunday))
               .Select(a => a.RepairHours).Sum() * RateWeekend), 2, MidpointRounding.AwayFromZero);
        }

我得到的錯誤：

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

我怎樣才能解決這個問題？

uj5u.com熱心網友回復：

DayOfWeek服務端不存在列舉，這是例外的根本原因。以下是解決問題的兩種解決方法。第一個使用作業日序數串列（0 和 6），第二個直接在條件中檢查序數（類似于您的原始方法）。

下面的示例適用于物體框架。DbFunctions.DiffDays對于 EFCore 支持，使用和EF.Functions.DateDiffDay作為各自的標準進行查找和替換。


private void SetTotalCharge()
{
    var dateTime = new DateTime(1899, 12, 31);
    var weekends = new List<int>{ 0, 6 };
    int.TryParse(MDate.ToString("MM"), out int month);
    int.TryParse(MDate.ToString("yyyy"), out int year);

    TotalCharge =
       Decimal.Round(Convert.ToDecimal(db.MyTable
       .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & !weekends.Any(r => r == DbFunctions.DiffDays(dateTime, a.Updated) % 7))
       .Select(a => a.RepairHours).Sum() * RateWeek
         db.MyTable
       .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & weekends.Any(r => r == DbFunctions.DiffDays(dateTime, a.Updated) % 7))
       .Select(a => a.RepairHours).Sum() * RateWeekend), 2, MidpointRounding.AwayFromZero);
}

或者

private void SetTotalCharge()
{
    var dateTime = new DateTime(1899, 12, 31);
    int.TryParse(MDate.ToString("MM"), out int month);
    int.TryParse(MDate.ToString("yyyy"), out int year);

    TotalCharge =
       Decimal.Round(Convert.ToDecimal(db.MyTable
       .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & ((DbFunctions.DiffDays(dateTime, a.Date) % 7) != 0 && (DbFunctions.DiffDays(dateTime, a.Date) % 7) != 6))
       .Select(a => a.RepairHours).Sum() * RateWeek
         db.MyTable
       .Where(a => a.Date <= MDate & a.Date.Month == MDate.Month & (a.Date.Year) == year & ((DbFunctions.DiffDays(dateTime, a.Date) % 7) == 0 || (DbFunctions.DiffDays(dateTime, a.Date) % 7) == 6))
       .Select(a => a.RepairHours).Sum() * RateWeekend), 2, MidpointRounding.AwayFromZero);
}

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