c# linq to objects Extract values between start and end strings

Question

            List<string> periods = new List<string>();
            periods.Add("2010 FYA");
            periods.Add("2011 FYA");
            periods.Add("2012 FYA");
            periods.Add("2013 FYA");
            periods.Add("1Q 2014A");
            periods.Add("2Q 2014A");
            periods.Add("3Q 2014A");
            periods.Add("4Q 2014A");
            periods.Add("2014 FYA");

            var xx = periods.Where(a => a.ToString() == "2010 FYA" && a.ToString() == "3Q 2014A").ToList();

IN LINQ there is no any between operator. so tell me how to use LINQ to extract data between two period.
i need to extract all data from period 2010 FYA to 3Q 2014A using LINQ. please show me how to achieve with LINQ. thanks

Answer 1

Try this approach:

string start = "2010 FYA";
string end = "3Q 2014A";

bool f = true;
var result = periods.SkipWhile( p => p != start ).TakeWhile( p => { bool b = f; f = p != end; return b; } );

Answer 2

An alternate is to use a language extension method, in this case if either item does not exists null is returned else a list is returned.

Caveats

• This code is case sensitive so if you lookfor 2010 FYA good while 2010 fYa will return -1 etc.
• I could had named BetweenItems Between but I have that already for a different usage.

My Between

public static bool Between<T>(this T value, T lowerValue, T upperValue) where T : struct, IComparable<T> => 
    Comparer<T>.Default.Compare(value, lowerValue) >= 0 && Comparer<T>.Default.Compare(value, upperValue) <= 0;

Demo

Demo

    private static void BetweenItems()
    {
        List<string> periods = new List<string>
        {
            "2010 FYA",
            "2011 FYA",
            "2012 FYA",
            "2013 FYA",
            "1Q 2014A",
            "2Q 2014A",
            "3Q 2014A",
            "4Q 2014A",
            "2014 FYA"
        };


        var result = periods.BetweenItems("2010 FYA", "3Q 2014A");
        if (result is not null)
        {
            foreach (var item in result)
            {
                Debug.WriteLine(item);
            }
        }
        else
        {
            Debug.WriteLine("Start or end value not located");
        }
    }

Returns

2010 FYA
2011 FYA
2012 FYA
2013 FYA
1Q 2014A
2Q 2014A
3Q 2014A

Extension class

public static class Extensions
{
    public static List<string> BetweenItems(this List<string> sender, string startValue, string endValue)
    {
        var startIndex = sender.IndexOf(startValue);
        var endIndex = sender.IndexOf(endValue) - startIndex +1;

        return startIndex == -1 || endIndex == -1 ? null : sender.GetRange(startIndex, endIndex);
    }
}

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