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

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

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)


<ExtensionAttribute> _
Public Shared Function Average(Of TSource) ( _
    source As IEnumerable(Of TSource), _
    selector As Func(Of TSource, Nullable(Of Double)) _
) As Nullable(Of Double)
public static Nullable<double> Average<TSource>(
    this IEnumerable<TSource> source,
    Func<TSource, Nullable<double>> selector

Type Parameters

  • TSource
    The type of the elements of source.


Return Value

Type: System..::.Nullable<(Of <(Double>)>)
The average of the sequence of values, or nullNothingnullptra null reference (Nothing in Visual Basic) if the source sequence is empty or contains only values that are nullNothingnullptra null reference (Nothing in Visual Basic).

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.


Exception Condition

source or selector is nullNothingnullptra null reference (Nothing in Visual Basic).


In Visual Basic query expression syntax, an Aggregate Into Average() clause translates to an invocation of Enumerable.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.
      outputBlock.Text &= "The average is " & avg & vbCrLf

      ' This code produces the following output:
      ' The average is 99948748093
      string[] numbers = { "10007", "37", "299846234235" };

      double average = numbers.Average(num => Convert.ToInt64(num));

      outputBlock.Text += String.Format("The average is {0}.", average) + "\n";

      // This code produces the following output:
      // The average is 99948748093. 

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0


Windows Phone

See Also


Enumerable Class

Average Overload

System.Linq Namespace