Group by with multiple columns using lambda

Question

How can I group by with multiple columns using lambda   I saw examples of how to do it using linq to entities  but I am looking for lambda form

User · Accepted Answer

var query   source GroupBy x   gt  new   x Column1  x Column2

User · Answer

Further to aduchis answer above - if you then need to filter based on those group by keys  you can define a class to wrap the many keys    return customers GroupBy a   gt  new CustomerGroupingKey a Country  a Gender                    Where a   gt  a Key Country     Ireland   amp  amp  a Key Gender     M                    SelectMany a   gt  a                   ToList      Where CustomerGroupingKey takes the group keys       private class CustomerGroupingKey               public CustomerGroupingKey string country  string gender                        Country   country              Gender   gender                     public string Country   get             public string Gender   get

User · Answer

if your table is like this  rowId     col1    col2    col3    col4  1          a       e       12       2  2          b       f       42       5  3          a       e       32       2  4          b       f       44       5   var grouped   myTable AsEnumerable   GroupBy r  gt  new  pp1    r Field lt int gt   col1    pp2   r Field lt int gt   col2

User · Answer

I came up with a mix of defining a class like David s answer  but not requiring a Where class to go with it   It looks something like   var resultsGroupings   resultsRecords GroupBy r   gt  new   r IdObj1  r IdObj2  r IdObj3                                        Select r   gt  new ResultGrouping                                           IdObj1  r Key IdObj1                                          IdObj2  r Key IdObj2                                          IdObj3  r Key IdObj3                                          Results   r ToArray                                            Count   r Count                                              private class ResultGrouping                       public short IdObj1  get  set                public short IdObj2  get  set                public int IdObj3  get  set                 public ResultCsvImport   Results   get  set                public int Count   get  set                Where resultRecords is my initial list I m grouping  and its a List lt ResultCsvImport gt    Note that the idea here to is that  I m grouping by 3 columns  IdObj1 and IdObj2 and IdObj3

User · Answer

class Element                       public string Company                      public string TypeOfInvestment              public decimal Worth                class Program               static void Main string   args                     List lt Element gt  elements   new List lt Element gt                                  new Element   Company    JPMORGAN CHASE  TypeOfInvestment    Stocks   Worth   96983                    new Element   Company    AMER TOWER CORP  TypeOfInvestment    Securities   Worth   17141                    new Element   Company    ORACLE CORP  TypeOfInvestment    Assets   Worth   59372                    new Element   Company    PEPSICO INC  TypeOfInvestment    Assets   Worth   26516                    new Element   Company    PROCTER  amp  GAMBL  TypeOfInvestment    Stocks   Worth   387050                    new Element   Company    QUASLCOMM INC  TypeOfInvestment    Bonds   Worth   196811                    new Element   Company    UTD TECHS CORP  TypeOfInvestment    Bonds   Worth   257429                    new Element   Company    WELLS FARGO-NEW  TypeOfInvestment    Bank Account   Worth   106600                    new Element   Company    FEDEX CORP  TypeOfInvestment    Stocks   Worth   103955                    new Element   Company    CVS CAREMARK CP  TypeOfInvestment    Securities   Worth   171048                                  Group by on multiple column in LINQ  Query Method              var query   from e in elements                         group e by new e TypeOfInvestment e Company  into eg                         select new  eg Key TypeOfInvestment  eg Key Company  Points   eg Sum rl   gt  rl Worth                   foreach  var item in query                                Console WriteLine item TypeOfInvestment PadRight 20          item Points ToString                                   Group by on multiple column in LINQ  Lambda Method              var CompanyDetails  elements GroupBy s   gt  new   s Company  s TypeOfInvestment                                   Select g   gt                                              new                                                                                               company   g Key Company                                                  TypeOfInvestment   g Key TypeOfInvestment                                                              Balance   g Sum x   gt  Math Round Convert ToDecimal x Worth   2                                                                                                       foreach  var item in CompanyDetails                                Console WriteLine item TypeOfInvestment PadRight 20          item Balance ToString                               Console ReadLine

[c#] Group by with multiple columns using lambda

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