如何在LINQ中减去两个日期？

Question

I have a problem with subtracting two dates in the MySQL database and comparing them to int numbers. I tried to use dbfunctions.diffdays however it is a conflict of types.

When I start the application I get a message:

System.ArgumentException: 'DbArithmeticExpression arguments must have a numeric common type.'

Below is my code i

    int intervalDay = 25;
    var dateCount = (from Rezerwacje in db.Rezerwacje
                     join rooms in db.rooms on Rezerwacje.PokojID equals rooms.id
                     where (rooms.floor > 0 && rooms.floor <= 2) &&(Rezerwacje.DataDo == dateTime) && ((Rezerwacje.DataDo - Rezerwacje.DataOd).Days > intervalDay)
                     select Rezerwacje).Count();
                     return dateCount;

Answer 1

You could use System.Data.Objects.EntityFucntions

and in the code:

where ... &&
      EntityFunctions.DiffDays(Rezerwacje.DataDo, Rezerwacje.DataOd) > intervalDay

Answer 2

 using System.Data.Entity;

 //code in LINQ
 ... DbFunctions.DiffDays(Rezerwacje.DataDo, Rezerwacje.DataOd) >= intervalDay

Answer 3

Ultimately I use List and foreach.

Downloading data from database:

public int DateCleanFloor1to2(DateTime dateTime)
{
            var dateList = (from Rezerwacje in db.Rezerwacje
                            join rooms in db.rooms on Rezerwacje.PokojID equals rooms.id
                            where (rooms.floor > 0 && rooms.floor <= 2) && (Rezerwacje.DataDo == dateTime)
                            select Rezerwacje).ToList();

            return SubtractDateToDateFrom(dateList, dateTime.AddDays(25));
 }

And method with foreach loop:

public int SubtractDateToDateFrom(List<Rezerwacje> dateList, DateTime dateTime)
{
            int count = 0;
            foreach (var item in dateList)
            {
                if (item.DataDo < dateTime)
                {
                    count++;
                }
            }

            return count;
}

@DevilSuichiro @Arulkumar @Seven