LINQ Query to Count Objects by Property Group Between Non Group Objects In Sequence

Question

I have a list of objects that have a sequence number property (Seq) and an InnerText property (among others). The objects are records (lines) in a text file.

Some records that have InnerText starting with 'X' have one or more continuation records after them that start with 'Y'. I want to add the info in the continuation records to the 'X' record object.

For each 'X' record I need to get a count of the succeeding 'Y' records stopping at the next instance of a non 'Y' record.

I need a way to count the 'Y' records in between the x.Seq record and the next non 'Y' record.

Here is what I have so far with the faulty LINQ statement:

public class File
{
    public Queue Records { get; set;}
}

public class Record
{
     public int Seq { get; set; }

     public string InnerText { get; set; }
}

foreach (Record record in Records)
{
    int recSeq = record.Seq;
        List<Record> aCopyOfRecords = records; 
        int numberOfYRecsFollowingX = aCopyOfRecords
        .Contains(element =>element.InnerText
        .StartsWith("Y") && (element.Seq > recSeq))).Count();
        for (int i = (recSeq + 1); i < (recSeq + numberOfYRecsFollowingX); i++)
    {
                Do Work adding fields etc...                            
    }
}

Thanks in advance for your help

Answer 1

You can use SkipWhile and TakeWhile methods

aCopyOfRecords
.SkipWhile(x => x != record)
.Skip(1)
.TakeWhile(x => x.InnerText.StartsWith("Y"));

This will give you the Y records that comes after specific record that starts with X.In order to get count, just use Count.If you want to insert new items to your list, use List<T>.Insert method:

var count =  aCopyOfRecords
           .SkipWhile(x => x != record) 
           .Skip(1)
           .TakeWhile(x => x.InnerText.StartsWith("Y"))
           .Count();

aCopyOfRecords.Insert(aCopyOfRecords.IndexOf(record) + count, newItem);