Average(TSource) Method (IEnumerable(TSource), Func(TSource, Double))

# Enumerable.Average(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Double))

.NET Framework 4.5

Computes the average of a sequence of 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

```<ExtensionAttribute>
Public Shared Function Average(Of TSource) (
source As IEnumerable(Of TSource),
selector As Func(Of TSource, Double)
) As Double
```

#### Parameters

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

A sequence of values to calculate the average of.

selector
Type: System.Func(Of TSource, Double)

A transform function to apply to each element.

#### Return Value

Type: System.Double

The average of the sequence of values.

#### Type Parameters

TSource

The type of the elements of source.

## Exceptions

Exception Condition
ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

## Remarks

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(Of TSource)(IEnumerable(Of TSource), Func(Of TSource, 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, change the body of the selector function.

```' Create an array of strings.
Dim numbers() As String = {"10007", "37", "299846234235"}

' Determine the average number after converting each
' string to an Int64 value.
Dim avg As Double = _
numbers.Average(Function(number) Convert.ToInt64(number))

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

' This code produces the following output:
'
' The average is 99948748093

```

## 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