如何使用實體框架按日期分組而不是日期與時間

Question

我的代碼：

//get data
var myData = from log in db.OperationLogs
              group log by log.CreateTime.Date  into g
              orderby g.Key
              select new { CreateTime = g.Key, Count = g.Count() };

此代碼將拋出異常，例如實體框架不支持獲取日期操作。 因為log.createtime都有日期和時間，我想按日期分組，我該怎么做

Answer 1

使用EntityFunctions.TruncateTime方法 ( Nullable<DateTime> ) 。 它將在生成的 SQL 查詢中轉換為TRUNCATETIME() TSQL 函數，它可以滿足您的需求：

返回表達式，時間值被截斷。

所以你的代碼應該如下：

//get data
var myData = from log in db.OperationLogs
             group log by EntityFunctions.TruncateTime(log.CreateTime) into g
             orderby g.Key
             select new { CreateTime = g.Key, Count = g.Count() };

Answer 2

這是為以后的實體框架版本執行此操作的更簡單方法。

var query = Data
.GroupBy(o => new { EventDate = o.EventDate.Date })
.Select(s => new SalesData()
{
    EventDate = s.Key.EventDate,
    Amount = s.Sum(o => o.Amount),
    Qty = s.Sum(o => o.Qty),
    RefundAmount = s.Sum(o => o.RefundAmount),
    RefundQty = s.Sum(o => o.RefundQty),
})
.OrderBy(o => o.EventDate)
.ToList();

返回查詢；

Answer 3

     var result = from s in entitiesModel.TvysFuelTankDatas
                           orderby s.Datetime ascending
                           group s by new { y = s.Datetime.Year, m = s.Datetime.Month + "/", d = s.Datetime.Day + "/" } into g
                           select new WellDrillData { Date = Convert.ToDateTime(g.Key.d.ToString() + g.Key.m.ToString() + g.Key.y.ToString()), Depth = (double)g.Sum(x => x.Difference) };

              List<WellDrillData> dailyFuelConsumptions = result.ToList();