Help with recursion and returning value

Question

This is an extension of a previously posted question. I'm trying to recursively build a string. I need to change the function below to do this - each recursion of the function generates the desired string, but I need to concat these together and return the whole string. 'related' is passed into the function as an empty string and I thought the way I was using string.Format would append each recursion to the 'related' string? Apparently not.

Not sure how...

private string getRelatedNews(Taxonomy taxData, string related, string contentTitle)
{
    foreach (TaxonomyItemData item in taxData.TaxonomyItems)
        {
            if (taxData.TaxonomyName.Equals(contentTitle) && taxData.TaxonomyItemCount != 0)
            {
                related = string.Format("{0}<li><a href='{1}'\">{2}</a></li>", related, item.Link, item.Name);
            }                   
        }
    // Show all its sub categories
    foreach (TaxonomyData cat in taxData.Taxonomy)
        {   
            getRelatedNews(cat, related, contentTitle);
        }

    return(related);

}

One issue with this is that you will be creating numerous strings that are thrown away (increasing pressure on the GC). Look into using StringBuilder to build a string only once. — Talljoe
– Talljoe, Commented Apr 8, 2011 at 4:19

JoDG · Accepted Answer · 2011-04-08 04:13:35Z

5

foreach (TaxonomyData cat in taxData.Taxonomy)
    {   
        getRelatedNews(cat, related, contentTitle);
    }

should be

foreach (TaxonomyData cat in taxData.Taxonomy)
    {   
        related = getRelatedNews(cat, related, contentTitle);
    }

because strings are immutable.

answered Apr 8, 2011 at 4:13

JoDG

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1 Comment

Nathan Over a year ago

Bingo. Gives exactly the result I expected. Thank you.

BenMorel · Accepted Answer · 2013-11-12 00:10:09Z

0

Well try this...

related = getRelatedNews(cat, related, contentTitle);

I am not sure about your logic and flow of the program... then also I think recursive function must be called like this....

private string getRelatedNews(Taxonomy taxData, string related, string contentTitle)
{
    foreach (TaxonomyItemData item in taxData.TaxonomyItems)
        {
            if (taxData.TaxonomyName.Equals(contentTitle) && taxData.TaxonomyItemCount != 0)
            {
                related = string.Format("{0}<li><a href='{1}'\">{2}</a></li>", related, item.Link, item.Name);
            }                   
        }
    // Show all its sub categories
    foreach (TaxonomyData cat in taxData.Taxonomy)
        {   
            related = getRelatedNews(cat, related, contentTitle);
        }

    return(related);

}

edited Nov 12, 2013 at 0:10

BenMorel

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answered Apr 8, 2011 at 4:14

Bhavik Goyal

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1 Comment

JoDG Over a year ago

he is alreadt concatenating using string.Format, you should not be doing related = related + string.Format....

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