# Enumerable.Average Method (IEnumerable(Of Nullable(Of Double)))

.NET Framework 4.5

Computes the average of a sequence of nullable Double values.

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

## Syntax

```'Declaration
<ExtensionAttribute> _
Public Shared Function Average ( _
source As IEnumerable(Of Nullable(Of Double)) _
) As Nullable(Of Double)
```

#### Parameters

source
Type: System.Collections.Generic.IEnumerable(Of Nullable(Of Double))

A sequence of nullable Double values to calculate the average of.

#### Return Value

Type: System.Nullable(Of Double)
The average of the sequence of values, or Nothing if the source sequence is empty or contains only values that are Nothing.

#### Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of Nullable(Of Double)). 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).

## Exceptions

ExceptionCondition
ArgumentNullException

source is Nothing.

## Remarks

If the sum of the elements is too large to represent as a Double, this method returns positive or negative infinity.

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

## Examples

The following code example demonstrates how to use Average(IEnumerable(Of Nullable(Of Int64))) to calculate an average.

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.

```        ' Create an array of nullable long values.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

' Determine the average value in the array.
Dim avg As Nullable(Of Double) = longs.Average()

' Display the output.
MsgBox("The average is " & avg.ToString)

' This code produces the following output:
'
' The average is 133282081426.333
```

## Version Information

#### .NET Framework

Supported in: 4.5.2, 4.5.1, 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

#### .NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

## Platforms

Windows Phone 8.1, Windows Phone 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.