i have a problem when filtering a list according to two dates in c#-CodePudding

var result = myList.Where(t =>  t.ReportDate >= StartDate)
                   .Where(t =>  t.ReportDate <= EndDate)

I'm trying to get all objects in a list (myList) thats have date (ReportDate) between StartDate and EndDate... I used the above code it worked good but when StartDate and EndDate are equals it returns null. can anyone help... thanks in advance.

CodePudding user response：

It seems, that you want to exclude time component:

var result = myList
  .Where(t => t.ReportDate.Date >= StartDate.Date &&
              t.ReportDate.Date <= EndDate.Date);

If it's your case, then when StartDate.Date == EndDate.Date you'll get result with ReportDate.Date == StartDate.Date

Please, note, that often it's more convenient to exclude the EndDate:

var result = myList
  .Where(t => t.ReportDate.Date >= StartDate.Date &&
              t.ReportDate.Date < EndDate.Date);

For instance, if we want 2021 year we can put 1.1.2021 .. 1.1.2022 instead of 1.1.2021 .. 31.12.2021

CodePudding user response：

The following sample code might put you on the right track

using System;
using System.Collections.Generic;

namespace Test
{
    class Program
    {
        static void Main()
        {
            List<DateTime> dateTimeList = new List<DateTime>
            {
                new DateTime(1946, 04, 11),
                new DateTime(1948, 04, 22),
                new DateTime(1975, 01, 23),
                new DateTime(1975, 01, 23),
                new DateTime(1977, 07, 07),
                new DateTime(1988, 05, 02),
            };
            DateTime beginDate = new DateTime(1970, 01, 01);
            DateTime endDate = new DateTime(1979, 12, 31);
            List<DateTime> result = dateTimeList.FindAll(x => x >= beginDate && x <= endDate);
            foreach (DateTime dateTime in result)
                Console.WriteLine(dateTime);
        }

    }
}

CodePudding user response：

I've done my best to incorporate your comments. This will ignore the time portion of the dates and will work with null ReportDates.

    DateTime now = DateTime.Now;
    // Get the Date part for the variables before the linq query
    DateTime startDate = now.Date;
    DateTime endDate = now.Date;
    
    List<Report> myList = new List<Report> { new Report(1, now), new Report(2, null), new Report(3, now.AddDays(1)) };

    // You are not required to make multiple Where calls
    // Check that ReportDate has a value before comparison
    // Get the Date part for the comparisons
    var reports = myList.Where(t => t.ReportDate.HasValue
                               && t.ReportDate.Value.Date >= startDate
                               && t.ReportDate.Value.Date <= endDate);
    
    foreach (var report in reports)
    {
        Console.WriteLine($"Report {report.ReportId}");
    }

Report 1