Btukfyl

Based on a list of a typed class like

class CostCenter

{

    string center;

    string percentage;

    DateTime start;

}

I have a list of these elements like this:

• {"a", 70, "2019/11/10"}


• {"b", 30, "2019/11/10"}


• {"A", 40, "2018/10/05"}


• {"B", 60, "2018/10/05"}


• {"xx", 10, "2010/01/01"}


• {"yy", 90, "2010/01/01"}


• {"100", 50, "2009/07/03"}


• {"101", 50, "2009/07/03"}

taking into account that I want to get rid of all of the elements (list) that have a start date earlier or equal than a fixed(_earliestDate), also this fixed data will replace the earliest match. In this example the earliest date is "2010/11/01", therefore "xx" and "yy" start date is replaced to "2010/11/01".
The output should be like this:

• {"a", 70, "2019/11/10"}


• {"b", 30, "2019/11/10"}


• {"A", 40, "2018/10/05"}


• {"B", 60, "2018/10/05"}


• {"xx", 10, "2010/11/01"}


• {"yy", 90, "2010/11/01"}

I have created the following code:

string dateToReplace = null;

bool earliestFound = false;

foreach (var item in list.OrderByDescending(x => DateTime.Parse(x.start)).ToList())

{

    if (earliestFound) //already marked, safe to remove others

    {

        list.Remove(item);

        continue;

    }



    if (!string.IsNullOrEmpty(dateToReplace)) //remaining matches

    {

        if (string.Equals(item.start, dateToReplace))

        {

            item.start = _earliestDate;

            continue;

        }

        else

        {

            earliestFound = true;

            list.Remove(item);

            continue;

        }

    }

    if (item.start <= _earliestDate) //first earliest or same, more required

    {

        dateToReplace = item.start;

        item.start = _earliestDate;

    }   

}

dateToReplace and earliestFound will be used as flags in the code to determine when to loop.

Somehow I think it is not the best option, do you have any suggestion on how to make it easier to understand or efficient?

To address the first part of your question : Removing items earlier that a given date.

Kiss is your best friend. either you reasign the list after a filtering or you remove all the item you don't want based on a predicate.

var inputs = new List<CostCenter> {

    new CostCenter("a", "70", "2019/11/10"),

    new CostCenter("b", "30", "2019/11/10"),

    new CostCenter("A", "40", "2018/10/05"),

    new CostCenter("B", "60", "2018/10/05"),

    new CostCenter("xx","10", "2010/01/01"),

    new CostCenter("yy", "90", "2010/01/01"),

    new CostCenter("100", "50", "2009/07/03"),

    new CostCenter("101", "50", "2009/07/03"),

};



var result1 = inputs.Where(x => x.start > DateTime.Parse("2010/01/01")).ToList();

var result2 = inputs.RemoveAll(x=> x.start <= DateTime.Parse("2010/01/01"));

First, you need to filter out all outdated items. Then, you can just take the first start, which is the earliest one, and then replace all with _earliestDate.

if (list == null)

    throw new ArgumentNullException(...);



// Get rid of unused items and sort:

var actual = list

    .Where(item => item.start >= _earliestDate)

    .OrderByDescending(item => item.start)

    .ToArray();



// If there are no matching items, then return empty array or throw exception

// It depends on your requirements

if (actual.Length == 0)

    return actual; 



// Take the least date in resulted array...

var earliestInActual = actual[actual.Length - 1]; 



// ...and replace it with _earliestDate

for (int i = actual.Length - 1; i >= 0; i--)

{

    if (actual[i].start != earliestInActual)

        break;



    item.start = _earliestDate;  

}



return actual;

Please, keep in mind that it will change original objects, therefore start dates will e updated in the original list as well.

Removing items from a list while using a foreach loop will cause it to lose it's position, you can however use a for loop or just do another loop removing all the flagged ones.

DateTime cutOffDate = DateTime.Parse("2010/11/01");



List<CostCenter> removeList = new List<CostCenter>();



foreach (var item in list.OrderByDescending(x => x.start).ToList())

{

    if (item.start <= cutOffDate) {

        removeList.Add(item);

    }

}



foreach(var remove in removeList)

{

    if (list.Contains(remove)) {

        list.Remove(remove);

    }

}

We can create new filtered list with given criteria

        DateTime threshold = new DateTime(2010, 11, 01);

        List<CostCenter> result = cc.Where(x => x.start.Date > threshold.Date).ToList();

POC : .netFiddle