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


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Computes the average of a 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)

Public Shared Function Average(Of TSource) (
	source As IEnumerable(Of TSource),
	selector As Func(Of TSource, Nullable(Of Double))
) As Nullable(Of Double)


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

A sequence of values to calculate the average of.

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

A transform function to apply to each element.

Return Value

Type: System.Nullable(Of Double)

The average of the sequence of values, or null if the source sequence is empty or contains only values that are null.

Type Parameters


The type of the elements of source.

Exception Condition

source or selector is null.

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.


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

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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