Count of each unique value in a list

Question

I need to find the unique values from a list and the number of times each value occurred in the original list. Here is what i have so far:

Dim Lister As New List(Of String)()

For Each item In eColumn
    Lister.Add(item.value)
Next

Dim Result As New List(Of String)
Result = Lister.Distinct().ToList

For Each st In Result
    MsgBox(st)
Next

The result is a list of all the unique values, but does not include a count for each item. For example, if my list was

John
John
Abbey
Larry
Larry
Larry
Charles

I want 4 values returned: John = 2, Abbey = 1,Larry = 3, Charles = 1.

[It does](https://msdn.microsoft.com/en-us/library/27b47ht3(v=vs.110).aspx). — GSerg, Sep 19 '16 at 22:21
@Plutonix I don't understand the link... I dont see where it says how I get a count of each unique item? — Chrisetiquette, Sep 19 '16 at 22:50
If `results` is a `List(Of String)` holding the unique items then, as the link clearly explains `results,Count` will be the number of unique items — Ňɏssa Pøngjǣrdenlarp, Sep 19 '16 at 23:26
Near duplicate of [LINQ to SQL using GROUP BY and COUNT(DISTINCT)](http://stackoverflow.com/a/449930/2592875) — TnTinMn, Sep 19 '16 at 23:32
@Plutonix You're missing what I am looking for. I need the count of how many of those items per value are in my list. — Chrisetiquette, Sep 19 '16 at 23:39
@Plutonix so if John is in the list two times, i need the number 2. — Chrisetiquette, Sep 19 '16 at 23:45

soohoonigan · Accepted Answer · 2016-09-20T01:19:21.990

Using linq's .Distinct() is only going to give you a list containing each distinct name in your list; so as you must have seen when your messagebox loop ran, it just shows you each name that is in your list once.

VB's lists do not have a native function for returning the count of an item's occurrences in a list, so to achieve your desired result just group them using linq's .GroupBy() function. It will return a Linq.GroupedEnumerable object, which can be iterated through and also possesses the kind of count property you're looking for:

    Dim myList As New List(Of String) From {"John", "John", "Abbey", "Larry", "Larry", "Larry", "Charles"}

    Dim groupedNames = myList.GroupBy(Function(x) x)
    If groupedNames IsNot Nothing AndAlso groupedNames.Count > 0 Then
        For Each person In groupedNames
            Debug.Print(person.Key & "-" & person.Count.ToString)
        Next
    End If

Output:

John-2
Abbey-1
Larry-3
Charles-1

Can you explain where the OP is having issues? Posting a solution that's doesn't explain why their code doesn't work isn't helpful... — Trevor, Sep 19 '16 at 23:57

Count of each unique value in a list

1 Answers1