How to get first record in each group using Linq

Question

Considering the following records      Id          F1            F2             F3   -------------------------------------------------    1           Nima          1990           10    2           Nima          1990           11    3           Nima          2000           12    4           John          2001           1    5           John          2002           2     6           Sara          2010           4   I want to group by based on the F1 field and sort by Id and get all fields from the first record of group similar to these records      Id          F1            F2             F3   -------------------------------------------------    1           Nima          1990           10    4           John          2001           1    6           Sara          2010           4   How can I do this using linq

User · Answer

Use it to achieve what you want  Then decide which properties you want to return   yourList OrderBy l   gt  l Id  GroupBy l   gt  new   GroupName   l F1   Select r   gt  r Key GroupName

User · Answer

var res    from element in list         OrderBy x   gt  x F2  AsEnumerable          GroupBy x   gt  x F1         Select    Use  AsEnumerable   after OrderBy

User · Answer

var res   from element in list               group element by element F1                   into groups                   select groups OrderBy p   gt  p F2  First

User · Answer

The awnser of  Alireza is totally correct  but you must notice that when using this code  var res   from element in list           group element by element F1               into groups               select groups OrderBy p   gt  p F2  First      which is simillar to this code because you ordering the list and then do the grouping so you are getting the first row of groups   var res    from element in list             OrderBy x   gt  x F2             GroupBy x   gt  x F1             Select     Now if you want to do something more complex like take the same grouping result but take the first element of F2 and the last element of F3 or something more custom you can do it by studing the code bellow   var res    from element in list             GroupBy x   gt  x F1             Select y   gt  new                           F1   y FirstOrDefault   F1               F2   y First   F2               F3   y Last   F3                   So you will get something like     F1            F2             F3   -----------------------------------    Nima          1990           12    John          2001           2    Sara          2010           4

User · Answer

var result   input GroupBy x  gt x F1  key g   gt g OrderBy e  gt e F2  First

[c#] How to get first record in each group using Linq

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