List of elements doesnt follow my recursion method c#

Question

I've got a method that calls itself (recursion). It collects some data which I need to analyse. It collects the data in a DTO. DTO setup:

    public class SequenceDTO
    {
        public string sequence { get; set; }
        public List<Element> stateList { get; set; }

        public SequenceDTO()
        { }

        public SequenceDTO(string sequence, List<Element> stateList)
        {
            this.sequence = sequence;
            this.stateList = stateList;
        }
    }

This is how I initialize the recursion method:

string seq = "";
List<Element> elmList = new List<Element>();
initialSeqDTO.sequence = seq;
initialSeqDTO.stateList = elmList;
analyze(element, initialSeqDTO); //The recursion method

The recursion method:

public void handleEventAnalysis3(Element elm, SequenceDTO dto)
{
    SequenceDTO newSeqDTO = new SequenceDTO();
    List<Element> elmList = new List<Element>();
    elmList = dto.stateList;
    newSeqDTO.sequence = dto.sequence;
    newSeqDTO.stateList = elmList;

    newSeqDTO.stateList.Add(clientElement);

    if (!clientElement.Name.Equals("Initial"))
         handleEventAnalysis3(clientElement, newSeqDTO);

    if (clientElement.Name.Equals("Initial"))
    {
        sequenceList.Add(newSeqDTO);
    }
}

This is adding SequenceDTO's to the sequenceList. But the dto.stateList is the same for every SequenceDTO. How can this be?

Yuval Itzchakov · Accepted Answer · 2014-11-11 15:34:23Z

2

You create a new List<Element>:

List<Element> elmList = new List<Element>();

But then you override it with the reference to your old list:

elmList = dto.stateList;

Instead, you can simply call ToList() to generate a new list:

newSeqDTO.stateList = dto.stateList.ToList();

answered Nov 11, 2014 at 15:34

Yuval Itzchakov

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1 Comment

n.Stenvang Over a year ago

Thought I had that covered with the new List<Element>() since it works with the sequence string. I will test it as the first thing in the morning (don't have the code near me) and then return with an accepted answer if it solved my problem.

Wiebe Tijsma · Accepted Answer · 2014-11-11 15:32:05Z

0

because you assign the same list to each DTO:

 elmList = dto.stateList; // this reassigns the variable which makes you lose the newly created list
 newSeqDTO.sequence = dto.sequence;
 newSeqDTO.stateList = elmList

It works if you just remove this line:

elmList = dto.stateList;

answered Nov 11, 2014 at 15:32

Wiebe Tijsma

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1 Comment

n.Stenvang Over a year ago

This will work for sure. But it doesn't cover my requirement which I might not have specified enough in the question. The list in the old DTO could contain something that I still want in the new and this is lost in your answer. Your answer just make a new list.

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