当试图按周分组时。只能从LINQ到实体调用此函数。 [英] When try to group by week. This function can only be invoked from LINQ to Entities.

问题描述

尝试执行以下操作时遇到的错误，将数据分组到linq到实体的周数。

The subjected error thrown when try to do the following, "Grouping data into weeks in linq to entity".

public object function(List<Students> stu)
{
var res=from p in stu
        where p.CurrentStatus=="Present"
        group p by (SqlFunction.DatePart("ww",p.AdmissionDate)) into Grp
        
        select new ResClass
        {
        label = Grp.Key.ToString(),
        fee  = Grp.Count(x=>x.fee)
         };
}

推荐答案

看看这里：http://stackoverflow.com/questions/1059737/group-by-weeks-in-linq-to-entities [ ^ ]

public object function(List<Students> stu)
{
var res=from p in stu
        where p.CurrentStatus=="Present"

//STEP 2: Use the function for Grouping as weekly

        group p by (Weekly(p.DateTime))) into Grp

//Step 2: if you want to group it by quarterly use replace above line with 
           
    group p by (Quarterly(p.DateTime.Value.Month)) into Grp

      

        select new ResClass
        {
        label = Grp.Key.ToString(),
        fee  = Grp.Count(x=>x.fee)
         };
}


//STEP 1: Make a Function for Week
 public int Weekly(DateTime day)
        {
            return System.Globalization.CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(day, System.Globalization.CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday);
        }

//Note if you want your data to group by quarterly use this function
        public int Quarterly(int month)
        {
            if (month == 1 || month == 2 || month == 3)
            {
                return 1;
            }
            if (month == 4 || month == 5 || month == 6)
            {
                return 2;
            }
            if (month == 7 || month == 8 || month == 9)
            {
                return 3;
            }
            else
            {
                return 4;
            }

        }

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