Sum(TSource) Method (IEnumerable(TSource), Func(TSource, Nullable(Double)))

# Enumerable::Sum<TSource> Method (IEnumerable<TSource>^, Func<TSource, Nullable<Double>>^)

.NET Framework 4.5

Computes the sum of the sequence of nullable Double 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)

## Syntax

```public:
generic<typename TSource>
[ExtensionAttribute]
static Nullable<double> Sum(
IEnumerable<TSource>^ source,
Func<TSource, Nullable<double>>^ selector
)
```

#### 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<Double>>^

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.

## Exceptions

Exception Condition
ArgumentNullException

source or selector is null.

## Remarks

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<Double> in C# or Nullable(Of Double) in Visual Basic.

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

## Examples

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.

## Version Information

Universal Windows Platform
Available since 4.5
.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

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