Artigo
11/18/2011

Enumerable.Average Method (IEnumerable<Nullable<Double>>)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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)

public static Nullable<double> Average(
    this IEnumerable<Nullable<double>> source
)

Parameters

source
Type: System.Collections.Generic.IEnumerable<Nullable<Double>>
A sequence of nullable Double values to calculate the average of.

Return Value

Type: System.Nullable<Double>
The average of the sequence of values, or nulla null reference (Nothing in Visual Basic) if the source sequence is empty or contains only values that are nulla 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<Nullable<Double>>. When you use instance method syntax to call this method, omit the first parameter.

Exceptions

Exception	Condition
ArgumentNullException	source is nulla null reference (Nothing in Visual Basic).

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<Nullable<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.
      outputBlock.Text &= "The average is " & avg.ToString & vbCrLf

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

      long?[] longs = { null, 10007L, 37L, 399846234235L };

      double? average = longs.Average();

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

      // This code produces the following output:
      //
      // The average is 133282081426.333.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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