Group By Multiple Columns

user_85952 0
Viewed 719938

How can I do GroupBy multiple columns in LINQ

Something similar to this in SQL:

SELECT * FROM <TableName> GROUP BY <Column1>,<Column2>

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
aggregate group-by linq .net c#
14 Answers

Use an anonymous type.

Eg

group x by new { x.Column1, x.Column2 }
user_155410

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 => t.Quantity)
                    }).ToList();
user_859520

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 => x.Quantity));

// or method syntax
var result2 = inMemoryTable.GroupBy(x => (x.Column1, x.Column2))
    .Select(g => (g.Key.Column1, g.Key.Column2, QuantitySum: g.Sum(x => 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 => x.Quantity) };

// or method syntax
var result4 = table.GroupBy(x => new { x.Column1, x.Column2 })
    .Select(g => 
      new { g.Key.Column1, g.Key.Column2 , QuantitySum= g.Sum(x => x.Quantity) });
user_42425900

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<DataRow> ClientProfiles = CurrentProfiles.AsEnumerable()
                        .Where(x => CheckProfileTypes.Contains(x.Field<object>(ProfileTypeField).ToString()));
// do other stuff, then check for dups...
                    var Dups = ClientProfiles.AsParallel()
                        .GroupBy(x => new { InterfaceID = x.Field<object>(InterfaceField).ToString(), ProfileType = x.Field<object>(ProfileTypeField).ToString() })
                        .Where(z => z.Count() > 1)
                        .Select(z => z);
user_1948720

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 => 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 => 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;
}
user_38504050

group x by new { x.Col, x.Col}

user_81853220

For VB and anonymous/lambda:

query.GroupBy(Function(x) New With {Key x.Field1, Key x.Field2, Key x.FieldN })
user_70988060
Related