Group By Multiple Columns

Question

How can I do GroupBy Multiple Columns in LINQ  Something similar to this in SQL    SELECT   FROM  lt TableName gt  GROUP BY  lt Column1 gt   lt Column2 gt    How can I convert this to LINQ   QuantityBreakdown       MaterialID int      ProductID int      Quantity float    INSERT INTO  QuantityBreakdown  MaterialID  ProductID  Quantity  SELECT MaterialID  ProductID  SUM Quantity  FROM  Transactions GROUP BY MaterialID  ProductID

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For VB and anonymous lambda   query GroupBy Function x  New With  Key x Field1  Key x Field2  Key x FieldN

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Though this question is asking about group by class properties  if you want to group by multiple columns against a ADO object  like a DataTable   you have to assign your  new  items to variables   EnumerableRowCollection lt DataRow gt  ClientProfiles   CurrentProfiles AsEnumerable                            Where x   gt  CheckProfileTypes Contains x Field lt object gt  ProfileTypeField  ToString         do other stuff  then check for dups                        var Dups   ClientProfiles AsParallel                            GroupBy x   gt  new   InterfaceID   x Field lt object gt  InterfaceField  ToString    ProfileType   x Field lt object gt  ProfileTypeField  ToString                               Where z   gt  z Count    gt  1                           Select z   gt  z

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A thing to note is that you need to send in an object for Lambda expressions and can t use an instance for a class   Example   public class Key       public string Prop1   get  set         public string Prop2   get  set        This will compile but will generate one key per cycle   var groupedCycles   cycles GroupBy x   gt  new Key      Prop1   x Column1     Prop2   x Column2       If you wan t to name the key properties and then retreive them you can do it like this instead  This will GroupBy correctly and give you the key properties   var groupedCycles   cycles GroupBy x   gt  new       Prop1   x Column1     Prop2  x Column2      foreach  var groupedCycle in groupedCycles        var key   new Key        key Prop1   groupedCycle Key Prop1      key Prop2   groupedCycle Key Prop2

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You can also use a Tuple lt   for a strongly-typed grouping   from grouping in list GroupBy x   gt  new Tuple lt string string string gt  x Person LastName x Person FirstName x Person MiddleName   select new SummaryItem       LastName   grouping Key Item1      FirstName   grouping Key Item2      MiddleName   grouping Key Item3      DayCount   grouping Count         AmountBilled   grouping Sum x   gt  x Rate

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var Results  query GroupBy f   gt  new      add members here

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Since C  7 you can also use value tuples   group x by  x Column1  x Column2    or   GroupBy x   gt   x Column1  x Column2

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C  7 1 or greater using Tuples and Inferred tuple element names  currently it works only with linq to objects and it is not supported when expression trees are required e g  someIQueryable GroupBy       Github issue       declarative query syntax var result        from x in inMemoryTable     group x by  x Column1  x Column2  into g     select  g Key Column1  g Key Column2  QuantitySum  g Sum x   gt  x Quantity        or method syntax var result2   inMemoryTable GroupBy x   gt   x Column1  x Column2        Select g   gt   g Key Column1  g Key Column2  QuantitySum  g Sum x   gt  x Quantity       C  3 or greater using anonymous types      declarative query syntax var result3        from x in table     group x by new   x Column1  x Column2   into g     select new   g Key Column1  g Key Column2  QuantitySum   g Sum x   gt  x Quantity         or method syntax var result4   table GroupBy x   gt  new   x Column1  x Column2         Select g   gt         new   g Key Column1  g Key Column2   QuantitySum  g Sum x   gt  x Quantity

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GroupBy x   gt   x MaterialID  x ProductID

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Procedural sample   GroupBy x   gt  new   x Column1  x Column2

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group x by new   x Col  x Col

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GroupBy x   gt  x Column1         x Column2

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For Group By Multiple Columns  Try this instead         GroupBy x  gt  new   x Column1  x Column2     key  group    gt  new       Key1   key Column1    Key2   key Column2    Result   group ToList          Same way you can add Column3  Column4 etc

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Ok got this as   var query    from t in Transactions              group t by new  t MaterialID  t ProductID               into grp                     select new                                               grp Key MaterialID                          grp Key ProductID                          Quantity   grp Sum t   gt  t Quantity                         ToList

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Use an anonymous type   Eg  group x by new   x Column1  x Column2

[c#] Group By Multiple Columns

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