Article
11/17/2011

Queryable.Average Method (IQueryable<Double>)

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Computes the average of a sequence of Double values.

Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Average ( _
    source As IQueryable(Of Double) _
) As Double

public static double Average(
    this IQueryable<double> source
)

Parameters

source
Type: System.Linq.IQueryable<Double>
A sequence of Double values to calculate the average of.

Return Value

Type: System.Double
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 IQueryable<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).
InvalidOperationException	source contains no elements.

Remarks

The Average(IQueryable<Double>) method generates a MethodCallExpression that represents calling Average(IQueryable<Double>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Double>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

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.

      Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

      Dim average As Double = grades.AsQueryable().Average()

      outputBlock.Text &= String.Format("The average grade is {0}.", average) & vbCrLf

      ' This code produces the following output:
      '
      ' The average grade is 77.6.

         List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

         double average = grades.AsQueryable().Average();

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

         // This code produces the following output:
         //
         // The average grade is 77.6.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

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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