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

.NET Framework 4.5

Computes the average of a sequence of Decimal 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)
```'Declaration
<ExtensionAttribute> _
Public Shared Function Average(Of TSource) ( _
source As IEnumerable(Of TSource), _
selector As Func(Of TSource, Decimal) _
) As Decimal
```

#### Type Parameters

TSource

The type of the elements of source.

#### Parameters

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

A sequence of values that are used to calculate an average.

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

A transform function to apply to each element.

#### Return Value

Type: System.Decimal
The average of the sequence of values.

#### Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of 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 Nothing.

InvalidOperationException

source contains no elements.

OverflowException

The sum of the elements in the sequence is larger than MaxValue.

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

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
```

#### .NET Framework

Supported in: 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

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.