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# Enumerable.Sum(TSource) Method (IEnumerable(TSource), Func(TSource, Nullable(Int64)))

.NET Framework 4.5

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)
```static member Sum :
source:IEnumerable<'TSource> *
selector:Func<'TSource, Nullable<int64>> -> Nullable<int64>
```

#### Type Parameters

TSource

The type of the elements of source.

#### Parameters

source
Type: System.Collections.Generic.IEnumerable(TSource)

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

selector
Type: System.Func(TSource, Nullable(Int64))

A transform function to apply to each element.

#### Return Value

Type: System.Nullable(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(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 a null reference (Nothing in Visual Basic).

OverflowException

The sum is larger than MaxValue.

This method returns zero if source contains no elements.

The result does not include values that are a null reference (Nothing in Visual Basic).

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(TSource)(IEnumerable(TSource), Func(TSource, Double)) 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.

No code example is currently available or this language may not be supported.

#### .NET Framework

Supported in: 4.5, 4, 3.5

#### .NET Framework Client Profile

Supported in: 4, 3.5 SP1

#### Portable Class Library

Supported in: Portable Class Library

#### .NET for Windows Store apps

Supported in: Windows 8

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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