Average(TSource) Method (IEnumerable(TSource), Func(TSource, Single))

Enumerable.Average<TSource> Method (IEnumerable<TSource>, Func<TSource, Single>)

Computes the average of a sequence of Single 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 static float Average<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, float> selector

Type Parameters


The type of the elements of source.


Type: System.Collections.Generic.IEnumerable<TSource>
A sequence of values to calculate the average of.
Type: System.Func<TSource, Single>
A transform function to apply to each element.

Return Value

Type: System.Single
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<TSource>. When you use instance method syntax to call this method, omit the first parameter.


source or selector is null.


source contains no elements.

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<TSource>(IEnumerable<TSource>, Func<TSource, Int32>) 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.

      string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

      double average = fruits.Average(s => s.Length);

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

      // This code produces the following output:
      // The average string length is 6.5. 


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

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

Community Additions

© 2015 Microsoft