Question

I’m currently developping an expression method (used in linq to entity queries) who has to give me

• a daycount for a given period (start date and end date)
• decrementing this daycount if specials days are in the period.

My idea was the following :

• Generate an enumerable with all the dates (and with Enumerable.Range)
• Make a .Where on this enumerable to remove the specials dates Like a MyEnumerable.Where(a => a != “20120101”)
• After that, return a MyEnumerable.Count()

I come with this code :

return (p) => Enumerable
                  .Range(1, 4)
                  .Where(a => a != 20120101)  
                  .AsQueryable()
                  .Count()

I tried to cast as a list, as a queryable, both (like the example) and no way ! it doesn’t work ! I always get this error :

LINQ to Entities does not recognize the method ‘System.Collections.Generic.IEnumerable`1[System.Int32] Range(Int32, Int32)’ method, and this method cannot be translated into a store expression.

Have you got an idea about that ?
Using an enumerable is of course not mandatory, any working solutions is good ^^

Thank’s by advance !

To simplify my question, this don’t works and i want to.

(
  from foo in User 
  select new 
  { 
    a = Enumerable.Range(1,4).Count() 
  }
).Take(1)

---

More informations 🙂

If i do this (externalize the enumerable in a variable) :

var foo = Enumerable.Range(1, 4);
return (p) => foo.Where(a => a != 20110101).Count();

This time it works, but i can’t define the range start and end with this method !

Answer 1

The code below generates a real DateTime range and will therefore correctly handle leap years, varying month ends, and so on. It also correctly handles daysToExclude being null or empty.

DateTime baseDate = DateTime.Now;
DateTime[] daysToExclude = new DateTime[] { new DateTime(2012, 6, 25), new DateTime(2012, 6, 30) } ;
int numberOfDays = baseDate.AddMonths(1).Subtract(baseDate).Days;

int days = Enumerable.Range(0, numberOfDays).Select(day => baseDate.Date.AddDays(day)).Except(daysToExclude ?? Enumerable.Empty<DateTime>()).Count();