EnumerableSum Method

Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

``````public static Nullable<long> Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, Nullable<long>> selector
)``````
``````public:
generic<typename TSource>
[ExtensionAttribute]
static Nullable<long long> Sum(
IEnumerable<TSource>^ source,
Func<TSource, Nullable<long long>>^ selector
)``````
``````static member Sum<'TSource> :
source:IEnumerable<'TSource> *
selector:Func<'TSource, Nullable<int64>> -> Nullable<int64>``````
``````<ExtensionAttribute>
Public Shared Function Sum(Of TSource) (
source As IEnumerable(Of TSource),
selector As Func(Of TSource, Nullable(Of Long))
) As Nullable(Of Long)``````

#### Parameters

source
Type:

A sequence of values that are used to calculate a sum.

selector
Type:

A transform function to apply to each element.

#### Return Value

Type:

The sum of the projected values.

#### Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source or selector is null.

OverflowException

The sum is larger than MaxValue.

This method returns zero if source contains no elements.

The result does not include values that are null.

You can apply this method to a sequence of arbitrary values if you provide a function, selector, that projects the members of source into a numeric type, specifically Nullable<Int64> in C# or Nullable(Of Int64) in Visual Basic

In Visual Basic query expression syntax, an Aggregate Into Sum() clause translates to an invocation of Sum.

The following code example demonstrates how to use Sum to sum the projected values of a sequence.

Note

This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. To extend the example to this topic, change the body of the selector function.

``````class Package
{
public string Company { get; set; }
public double Weight { get; set; }
}

public static void SumEx1()
{
List<Package> packages =
new List<Package>
{ new Package { Company = "Coho Vineyard", Weight = 25.2 },
new Package { Company = "Lucerne Publishing", Weight = 18.7 },
new Package { Company = "Wingtip Toys", Weight = 6.0 },
new Package { Company = "Adventure Works", Weight = 33.8 } };

double totalWeight = packages.Sum(pkg => pkg.Weight);

Console.WriteLine("The total weight of the packages is: {0}", totalWeight);
}

/*
This code produces the following output:

The total weight of the packages is: 83.7
*/
``````
``````Structure Package
Public Company As String
Public Weight As Double
End Structure

Sub SumEx1()
' Create a list of Package values.
Dim packages As New List(Of Package)(New Package() _
{New Package With {.Company = "Coho Vineyard", .Weight = 25.2},
New Package With {.Company = "Lucerne Publishing", .Weight = 18.7},
New Package With {.Company = "Wingtip Toys", .Weight = 6.0},
New Package With {.Company = "Adventure Works", .Weight = 33.8}})

' Sum the values from each item's Weight property.
Dim totalWeight As Double = packages.Sum(Function(pkg) _
pkg.Weight)

' Display the result.
MsgBox("The total weight of the packages is: " & totalWeight)
End Sub

' This code produces the following output:
'
' The total weight of the packages is: 83.7
``````
Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1