Applying Group By in LINQ

Question

I decided to group the collection by length of the string.Need suggestion from you to correct myself.

        string[] collection = {"five","four","ten","one"};

        var GroupedValues =
                    from w in collection
                    group w by w.Length into GetByGroup
                    select GetByGroup;

        foreach (var g in GroupedValues)
        {
            Console.WriteLine(g);
        }

The output is :

System.Linq.Lookup....

System.Linq.Lookup....

What went wrong ?

Answer 1

GroupBy returns a Lookup object which contains the Key and the collection in the grouping.

foreach (var g in GroupedValues)
{
    Console.WriteLine("There are {1} strings of length {0}.", g.Key, g.Count());
    foreach (var v in g)
    {
        Console.WriteLine(" - {0}", v);
    }
}

Answer 2

What went wrong depends on what you wanted to do!

The sequence you get back after grouping is not a flat sequence of the original objects (so in your case, it's not a sequence of strings). Otherwise how would they have been grouped?

Maybe given that you apparently expected a flat list of strings, you actually wanted to order them by length:

var collection = new[] {"five","four","ten","one"};

var byLength = collection.OrderBy(s => s.Length);

foreach (var s in GroupedValues)
    Console.WriteLine(s);

Or if you wanted to group them, then you have to deal with each group in turn, and each group is a separate list of strings:

foreach (var g in GroupedValues)
{
    Console.WriteLine("Strings of length " + g.Key + ":");

    foreach (var s in g) 
        Console.WriteLine("    " + s);
}