Grouping Strings and Adding into a list

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I have a List that has strings something like this

"Category1/SubType1"
"Category1/SubType2"
"Category1/SubType3"  
"Category1/SubType4" 
"Category2/SubType1"
"Category2/SubType2"   
"Category2/SubType3" 
"Category2/SubType4"
"Category3"
"Category4"
"Category4/SubType1"
"Category4/SubType2

i have a class that has two properties.

public class CategoriesClass
    {
        public CategoriesClass(string category, List<string> subCategory)
        {
            this.category = category;
            this.subCategory = subCategory.ToArray();
        }
        public string category { get; private set; }
        public string[] subCategory { get; private set; }
    }

I need to iterate through the list, and pick all the categories and then add subcategories to them.
Not all Categories have Sub Categories. So, the categories which don't have sub categories will have subcategory as null. And Some categories (like category 4 will have just the category name and then its sub categories)
I had sorted the list and I was able to achieve the traditional way by doing a for loop by taking the first string and comparing with the rest. I was wondering if there is any neater way to do this?

Posted 18-Dec-13 17:06pm

Member 10475792

Updated 18-Dec-13 17:17pm

v3

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BillWoodruff 19-Dec-13 7:29am

Perhaps a Linq expert will come along and put a mind-blowingly terse solution here, but, in the meantime, unless we know how you coded the for-loop solution, we can't compare it with alternative approaches, or offer alternative ideas.

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Christopher Drake · Answer 1 · 2013-12-19T05:24:00

You could try something like this:

C#

internal class Cat{
    public string category;
    public string sub;
}

static void Main(string[] args)
{
    string[] categories = {
        "Category1/SubType1",
        "Category1/SubType2",
        "Category1/SubType3",
        "Category1/SubType4",
        "Category2/SubType1",
        "Category2/SubType2",
        "Category2/SubType3",
        "Category2/SubType4",
        "Category3",
        "Category4",
        "Category4/SubType1",
        "Category4/SubType2"};

    Dictionary<string, List<Cat>> categoryDict = categories.Select(c => c.Split('/'))
    .Select(a => new Cat()
    {
        category = a[0],
        sub = a.Length > 1 ? a[1] : string.Empty
    })
    .GroupBy(b => b.category)
    .ToDictionary(e => e.Key, e => e.ToList());

}

Member 10475792 · Answer 2 · 2013-12-19T05:49:00

I had a got a solution from different source.Had to modify it a bit.. But this worked . Posting it here for others..

C#

list.Select(item => item.Split('/'))
    .GroupBy(tokens => tokens[0], tokens => tokens[1])
    .Select(g => new TheClass
                     {
                         Category = g.Key,
                         SubCategory = g.ToList()
                     });

Grouping Strings and Adding into a list

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