Question

I have to compare three dates in linq query (datetime a < datetime b < datetime c), but just properties month and day. How can i do it?

Answer 1

You may create a new datetime with the current year:

var year = DateTime.Now.Year;
var dateATemp = new DateTime(year, dateA.Month, dateA.Day);
var dateBTemp = new DateTime(year, dateB.Month, dateB.Day);
var dateCTemp = new DateTime(year, dateC.Month, dateC.Day);

Now compare dateATemp < dateBTemp < dateCTemp

You could write an extension method from DateTime that will return you a new DateTime instance with the current year:

public static DateTime ToDateTimeWithCurrentYear(this DateTime value)
{
    return new DateTime(DateTime.Now.Year, value.Month, value.Day);
}

and use it like this:

dateA.ToDateTimeWithCurrentYear() < dateB.ToDateTimeWithCurrentYear() < dateC.ToDateTimeWithCurrentYear()