ansaurus

Question

Need help with a Linq XML conditional grouping query

Answer 1

A:

Consider calculating a relatable value (position) as in the example below.

public class TopTitle
{
  public int Span {get;set;}
  public string Value {get;set;}
  public int Position {get;set;}
}

public class SubTitle
{
  public int Span {get;set;}
  public string Value {get;set;}
  public int Position {get;set;}
}

//
List<Title> Titles = GetTitles();
List<SubTitle> SubTitles = GetSubTitles();
int i = 0;
Titles.ForEach(t =>
{
  t.Position = i;
  i += t.Span;
}
i = 0;
SubTitles.ForEach(st =>
{
  st.Position = i;
  i += st.Span;
}

var query =
  from t in Titles
  let sts =
    from st in SubTitles
    where t.Position <= st.Position
      && st.Position < (t.Position + t.Span)
  select st
  select new {Title = t, SubTitles = sts.ToList()};

David B 2010-05-04 20:32:04

Answer 2

A:

Maybe you could utilise the following by expanding on the criteria selection:

public class Grouping
{
    public string Title { get; set; }
    public string Criteria { get; set; }
}


XmlDocument xDoc = new XmlDocument();

var First_Sequence = (from b in XElement.Load("Banners.xml").Elements("BANNER_TEXTS").First().Elements("BANNER_TEXT")
                              where b.Value != ""
                              select b);

var Second_Sequence = (from b in XElement.Load("Banners.xml").Elements("BANNER_TEXTS").Skip(1).First().Elements("BANNER_TEXT")
                               where b.Value != "Total"
                               select b).ToList();

List<Grouping> groups = new List<Grouping>();

int i = 0;
foreach (var item in First_Sequence)
{
    groups.Add(new Grouping { Title = item.Value, Criteria = (Second_Sequence.Skip(i).First().Value).ToString() });
    i++;
}

Nicholas Murray 2010-05-04 22:34:52

Answer 3

A:

This should iterate each sequence (the header sequence and the values sequence) once:

static IEnumerable<IGrouping<TFirst, TSecond>> Chunk<TFirst, TSecond>(
    IEnumerable<TFirst> source, 
    IEnumerable<TSecond> toChunk, 
    Func<TFirst, int> chunkSizeSelector)
{
    //error checking here
    using (var chunkItems = toChunk.GetEnumerator())
    {
        foreach (var key in source)
        {
            List<TSecond> items = new List<TSecond>();
            for (int itemsRemaining = chunkSizeSelector(key); itemsRemaining > 0; itemsRemaining--)
            {
                if (!chunkItems.MoveNext())
                    throw new ArgumentException("There are not enough items in toChunk to satisfy source.");
                items.Add(chunkItems.Current);
            }
            yield return new ChunkGrouping<TFirst, TSecond>(key, items);
        }
    }
}

internal class ChunkGrouping<TKey, TElement> : IGrouping<TKey, TElement>
{
    public ChunkGrouping(TKey key, IEnumerable<TElement> elements)
    {
        if (elements == null) throw new ArgumentNullException("elements");
        _key = key;
        _elements = elements;
    }

    private readonly TKey _key;
    private readonly IEnumerable<TElement> _elements;

    public TKey Key { get { return _key; } }

    IEnumerator<TElement> IEnumerable<TElement>.GetEnumerator()
    {
        return _elements.GetEnumerator();
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return _elements.GetEnumerator();
    }
}

Then you can use it as:

foreach (var group in Chunk(child.Elements("BANNER_TEXTS").ElementAt(0).Elements(),
                            child.Elements("BANNER_TEXTS").ElementAt(1).Elements(),
                            xe => (int)xe.Attribute("SPAN_COL")))
{
    //do stuff with the elements
}

Gideon Engelberth 2010-05-05 00:05:30

Answer 4

A:

I ended up using this:

foreach (XElement child in e.Elements("BANNER"))
            {

                IEnumerable<XElement> groups = child.Descendants("BANNER_TEXTS").ElementAt(0).Descendants("BANNER_TEXT");

                var groupCats =
                from s in groups
                group s by s.Value into grouped
                select new
                {
                    GroupCategory = grouped.Key,
                    Categories = GetCategories(grouped.Key, child)
                };
            }

 private IEnumerable<string> GetCategories(string key, XElement parent)
    {
        int span = parent.Descendants("BANNER_TEXTS").ElementAt(0).Descendants("BANNER_TEXT").Where(x => x.Value == key).Select(x => int.Parse(x.Attribute("SPAN_COL").Value)).FirstOrDefault();
        IEnumerable<int> set = Series(key,parent.Descendants("BANNER_TEXTS").ElementAt(0).Descendants("BANNER_TEXT"));
        int sum = set.Sum();        
        return parent.Descendants("BANNER_TEXTS").ElementAt(1).Descendants("BANNER_TEXT").Skip(sum).Take(span).Select(x => x.Value);

    }

    private static IEnumerable<int> Series(string key, IEnumerable<XElement> elements)
    {

        foreach (XElement item in elements)
        {
            if (item.Value != key)
            {
                yield return int.Parse(item.Attribute("SPAN_COL").Value);

            }
            else
            {
                break;
            }

        }

    }

FiveTools 2010-05-05 01:16:38

I don't know why I didn't use a method call in the first place. Thanks for everyone's help. All these samples got me thinking.

FiveTools 2010-05-05 01:35:16

@FiveTools: Don't forget to mark this as the correct answer if this is what you used

Alastair Pitts 2010-05-05 02:02:54

ansaurus

tags:

views:

answers:

Need help with a Linq XML conditional grouping query

related questions