LINQ with groupby and count

Question

This is pretty simple but I m at a loss  Given this type of data set  UserInfo name  metric  day  other metric   and this sample data set  joe  1 01 01 2011 5 jane 0 01 02 2011 9 john 2 01 03 2011 0 jim  3 01 04 2011 1 jean 1 01 05 2011 3 jill 2 01 06 2011 5 jeb  0 01 07 2011 3 jenn 0 01 08 2011 7  I d like to retrieve a table that lists metrics in order 0 1 2 3    with the total number of times the count occurs  So from this set  you d end up with  0 3     1 2     2 2     3 1  I m grappling with the LINQ syntax but am stuck on where to put a groupby and count    any help  POST Edit  I was never able to get the posted answers to work as they always returned one record with the number of different counts  However  I was able to put together a LINQ to SQL example that did work  var pl   from r in info          orderby r metric              group r by r metric into grp          select new   key   grp Key  cnt   grp Count      This result gave me an ordered set of records with  metrics  and the number of users associated with each  I m clearly new to LINQ in general and to my untrained eye this approach seems very similar to the pure LINQ approach yet gave me a different answer

User · Answer

userInfos GroupBy userInfo   gt  userInfo metric           OrderBy group   gt  group Key           Select group   gt  Tuple Create group Key  group Count

User · Answer

Assuming userInfoList is a List lt UserInfo gt            var groups   userInfoList              GroupBy n   gt  n metric               Select n   gt  new                               MetricName   n Key                  MetricCount   n Count                                            OrderBy n   gt  n MetricName     The lambda function for GroupBy    n   gt  n metric means that it will get field metric from every UserInfo object encountered  The type of n is depending on the context  in the first occurrence it s of type UserInfo  because the list contains UserInfo objects  In the second occurrence n is of type Grouping  because now it s a list of Grouping objects   Groupings have extension methods like  Count     Key   and pretty much anything else you would expect  Just as you would check  Lenght on a string  you can check  Count   on a group

User · Answer

After calling GroupBy  you get a series of groups IEnumerable lt Grouping gt   where each Grouping itself exposes the Key used to create the group and also is an IEnumerable lt T gt  of whatever items are in your original data set  You just have to call Count   on that Grouping to get the subtotal  foreach var line in data GroupBy info   gt  info metric                           Select group   gt  new                                 Metric   group Key                                Count   group Count                                                        OrderBy x   gt  x Metric          Console WriteLine  quot  0   1  quot   line Metric  line Count         This was a brilliantly quick reply but I m having a bit of an issue with the first line  specifically  data groupby info  info metric   I m assuming you already have a list array of some class that looks like class UserInfo       string name      int metric        etc          List lt UserInfo gt  data            When you do data GroupBy x   gt  x metric   it means  quot for each element x in the IEnumerable defined by data  calculate it s  metric  then group all the elements with the same metric into a Grouping and return an IEnumerable of all the resulting groups  Given your example data set of      lt DATA gt              Grouping Key  x  gt x metric    joe  1 01 01 2011 5    1 jane 0 01 02 2011 9    0 john 2 01 03 2011 0    2 jim  3 01 04 2011 1    3 jean 1 01 05 2011 3    1 jill 2 01 06 2011 5    2 jeb  0 01 07 2011 3    0 jenn 0 01 08 2011 7    0  it would result in the following result after the groupby   Group 1    joe  1 01 01 2011 5  jean 1 01 05 2011 3   Group 0    jane 0 01 02 2011 9  jeb  0 01 07 2011 3  jenn 0 01 08 2011 7   Group 2    john 2 01 03 2011 0  jill 2 01 06 2011 5   Group 3    jim  3 01 04 2011 1

[c#] LINQ with groupby and count

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