How to get value from List<List<string>>

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Hi I have following collection

C#

List<List<string>> Test_List = new List<List<string>>();

           List<string> a = new List<string> { "1", "2", "1", "1", "3" };
           List<string> b = new List<string>{ "11", "12", "11", "11", "13" };
           List<string> c = new List<string>{ "21", "22", "21", "21", "23" };
           List<string> d = new List<string> { "31", "32", "31", "31", "33" };

           Test_List.Add(a);
           Test_List.Add(b);
           Test_List.Add(c);
           Test_List.Add(d);

I want to get a new list that would contain a value repeated highest time in each element of Test_list for e.g. In above case a,b,c,d are element of Test_list, we see 1 has repeated highest time in a, like wise 11 in b, 21 in c and 31 in d.
I want to get a new list or array that would contain 1,11,21,31 in it. I want Linq solution without any loop.

I tried with

C#

var res = Test_List.Select(n=>n).Select(l=>l).GroupBy(m => m).Select(g => new { count = g.Count(), value = g.Key }).OrderByDescending(u=> u.count).Select(h=>h.value).ToArray();

But above code did not work for me.
Thanks

Posted 15-May-14 8:24am

rameshKumar1717

Updated 15-May-14 9:09am

CPallini

v2

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3 solutions

Solution 3

Another approach, 2 steps, straightforward logic, maybe it does the job for someone

C#

Test_List.ForEach(p => p.Sort((x, y) => p.Count(s => s == y).CompareTo(p.Count(s => s == x))));
var q = Test_List.Select(p => p.First()).ToList();

Posted 15-May-14 9:20am

Emre Ataseven

Updated 15-May-14 9:34am

v2

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OriginalGriff · Accepted Answer · 2014-05-15T08:47:00

Solution 1

You were nearly there:

C#

var res = Test_List.Select(tl => tl.GroupBy(t => t).Select(g => new { val = g.Key, cnt = g.Count() }).OrderByDescending(o => o.cnt).ToArray()[0].val);

Posted 15-May-14 8:47am

OriginalGriff

Comments

Sander Rossel 15-May-14 15:06pm

My vote of 1, you just beat me to it (j/k gave a 5)! ;-)
I guess more or less the same solution as I have, just written differently :-)

rameshKumar1717 17-May-14 2:13am

This solution exactly I was looking for single line without any loop. thanks

OriginalGriff 17-May-14 2:26am

You're welcome!

Sander Rossel · Accepted Answer · 2014-05-15T08:55:00

Well, one solution could be the following:

C#

List<string> doubles = Test_List.SelectMany(l => l).ToLookup(s => s).Where(g => g.Count() > 1).Select(g => g.Key).ToList();

// Complete step-by-step explanation:

// First we use SelectMany to combine the strings in all our lists to a single list.
IEnumerable<string> first = Test_List.SelectMany(l => l);
// Next we create a lookup, having the string as a key and all the occurrences of that string as a value.
ILookup<string, string> next = first.ToLookup(s => s);
// After that we filter this lookup grabbing all entries that has more than 1 value (meaning more than one
// occurrence in the original list).
IEnumerable<IGrouping<string, string>> afterThat = next.Where(g => g.Count() > 1);
// Then we select the original string, using the keys of the lookup.
IEnumerable<string> then = afterThat.Select(g => g.Key);
// Last we create a list (or array) to hold the items. You could add ordering etc.
List<string> last = then.ToList();

I'm not saying this is the best way to do it (with LINQ there are usually more methods to get to the same result), but it's one solution and I think it's not to hard to understand :)