Enumerable.Sum(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Int64))

Computes the sum of the sequence of 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)

'Declaration
<ExtensionAttribute> _
Public Shared Function Sum(Of TSource) ( _
	source As IEnumerable(Of TSource), _
	selector As Func(Of TSource, Long) _
) As Long

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable(Of TSource)
A sequence of values that are used to calculate a sum.
selector
Type: System.Func(Of TSource, Int64)
A transform function to apply to each element.

Return Value

Type: System.Int64
The sum of the projected values.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of TSource). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

source or selector is Nothing.

OverflowException

The sum is larger than MaxValue.

This method returns zero if source contains no elements.

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 Int64.

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(Of TSource)(IEnumerable(Of TSource), Func(Of TSource, Double)) to sum the projected values of a sequence.

NoteNote

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.


    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



.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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