A method to count occurrences in a list

Question

Is there a simple way to count the number of occurrences of all elements of a list into that same list in C     Something like this   using System  using System IO  using System Text RegularExpressions  using System Collections Generic  using System Linq   string Occur  List lt string gt  Words   new List lt string gt     List lt string gt  Occurrences   new List lt string gt          170 elements added        for  int i   0 i lt Words Count i         Words   Words Distinct   ToList        for  int ii   0 ii lt Words Count ii    Occur   new Regex Words ii   Matches Words    Count            Occurrences Add  Occur            Console Write   0    1       Words i   Occurrences i

User · Answer

public void printsOccurences List lt String gt  words        var selectQuery           from word in words         group word by word into g         select new  Word   g Key  Count   g Count         foreach var word in selectQuery          Console WriteLine    word Word    word Count     emphasized text

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Your outer loop is looping over all the words in the list  It s unnecessary and will cause you problems  Remove it and it should work properly

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You can do something like this to count from a list of things   IList lt String gt  names   new List lt string gt       ToString    Format     IEnumerable lt String gt  methodNames   typeof String  GetMethods   Select x   gt  x Name    int count   methodNames Where x   gt  names Contains x   Count      To count a single element  string occur    Test1   IList lt String gt  words   new List lt string gt      Test1   Test2   Test3   Test1     int count   words Where x   gt  x Equals occur   Count

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How about something like this      var l1   new List lt int gt      1 2 3 4 5 2 2 2 4 4 4 1     var g   l1 GroupBy  i   gt  i     foreach  var grp in g       Console WriteLine    0   1    grp Key  grp Count          Edit per comment   I will try and do this justice      In my example  it s a Func lt int  TKey gt  because my list is ints   So  I m telling GroupBy how to group my items   The Func takes a int and returns the the key for my grouping   In this case  I will get an IGrouping lt int int gt   a grouping of ints keyed by an int    If I changed it to  i   gt  i ToString     for example  I would be keying my grouping by a string   You can imagine a less trivial example than keying by  1    2    3      maybe I make a function that returns  one    two    three  to be my keys      private string SampleMethod  int i          magically return  One  if i    1   Two  if i    2  etc      So  that s a Func that would take an int and return a string  just like      i   gt      magically return  One  if i    1   Two  if i    2  etc     But  since the original question called for knowing the original list value and it s count  I just used an integer to key my integer grouping to make my example simpler

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var wordCount       from word in words     group word by word into g     select new   g Key  Count   g Count            This is taken from one of the examples in the linqpad

[c#] A method to count occurrences in a list

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