Sum Method (IEnumerable(Nullable(Double)))

# Enumerable.Sum Method (IEnumerable<Nullable<Double>>)

Computes the sum of a sequence of nullable Double values.

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

## Syntax

```public static Nullable<double> Sum(
this IEnumerable<Nullable<double>> source
)
```

#### Parameters

source
Type: System.Collections.Generic.IEnumerable<Nullable<Double>>
A sequence of nullable Double values to calculate the sum of.

#### Return Value

Type: System.Nullable<Double>
The sum of the values in the sequence.

#### Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<Nullable<Double>>. When you use instance method syntax to call this method, omit the first parameter.

## Exceptions

ExceptionCondition
ArgumentNullException

source is null.

## Remarks

This method returns zero if source contains no elements.

The result does not include values that are null.

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

## Examples

The following code example demonstrates how to use Sum(IEnumerable<Nullable<Single>>) to sum the 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, substitute the elements of the source sequence with elements of the appropriate numerical type.

```
float?[] points = { null, 0, 92.83F, null, 100.0F, 37.46F, 81.1F };

float? sum = points.Sum();

outputBlock.Text += String.Format("Total points earned: {0}", sum) + "\n";

/*
This code produces the following output:

Total points earned: 311.39
*/

```

## Version Information

#### Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone