Question

Given sequence :

["1","A","B","C","2","F","K","L","5","6","P","I","E"]

The numbers represent items that I identify as headers, whereas the letters represent items that I identify as data. I want to associate them into groups like this.

1:A,B,C    
2:F,K,L    
5:    
6:P,I,E

I can easily achieve this using a foreach or while loop on the enumerator, but is there a LINQ’ish way to achieve this? This is a recurring pattern in my domain.

Answer 1

You can make use of a fold:

var aggr = new List<Tuple<Int,List<String>>>();
var res = sequence.Aggregate(aggr, (d, x) => {
    int i;
    if (Int32.TryParse(x, out i)) {
        var newDict = d.Add(new Tuple(i, new List<string>()));
        return newDict;
    } 
    else {
        var newDict = d[d.Count - 1].Item2.Add(x);
        return newDict;
    }
}).ToDictionary(x => x.Item1, x => x.Item2);

However, this doesn’t look so nice, since there’s lacking support for immutable values. Also, I couldn’t test this right now.