Linq comparing 2 dates

Question

I am trying to compare date only. The value in table is DateTime with format 2014-01-29 09:00:00.000. Please advise thank you

public static List<vwReportDate> GetDetail(string startDate, string endDate)
{
    startDate = "2014-01-28";
    endDate = "2014-01-28";

    DateTime dtStart = Convert.ToDateTime(startDate);
    DateTime dtEndDate = Convert.ToDateTime(endDate);


    var entities = new DataEntiies();
    var query = from c in entities.vwReportDate
                where c.EventCreateDate >= dtStart && c.EventCreateDate <= dtEndDate
                select c;
    return query.ToList();

}

Answer 1

It looks like you're using Entity Framework and LINQ to EF. If that's true you can't use DateTime.Date property because it's not supported in LINQ to EF. You have to use EntityFunctions.TruncateTime(myDateTime) static method instead:

var query = from c in entities.vwReportDate
            let eventDate = EntityFunctions.TruncateTime(c.EventCreateDate)
            where eventDate >= dtStart && eventDate <= dtEndDate
            select c;

Answer 2

My approach to this problem, which does not depend on EF, is to use "less than" for the end of the date range (after moving the end of the date range one day forward):

startDate = "2014-01-28";
endDate = "2014-01-28";

DateTime dtStart = Convert.ToDateTime(startDate);
DateTime dtEndDate = Convert.ToDateTime(endDate).AddDays(1);


var entities = new DataEntiies();
var query = from c in entities.vwReportDate
            where c.EventCreateDate >= dtStart && c.EventCreateDate < dtEndDate
            select c;
return query.ToList();

Question: why do you ignore the argument values provided by the method's caller?

Answer 3

Use the Date property of a DateTime struct to retrieve the "date" part.

Gets the date component of this instance.

Use it in code:

var query = from c in entities.vwReportDate
            where c.EventCreateDate.Date >= dtStart && c.EventCreateDate.Date <= dtEndDate
            select c;

If you are using Entity framework (as it looks like you do), you'll have to use the EntityFunctions.TruncateTime (helper) method, because otherwise the query can't be converted.

var query = from c in entities.vwReportDate
            where EntityFunctions.TruncateTime(c.EventCreateDate) >= dtStart && EntityFunctions.TruncateTime(c.EventCreateDate) <= dtEndDate
            select c;