Enumerable.Average<TSource> Method (IEnumerable<TSource>, Func<TSource, Int32>)

July 28, 2014

Computes the average of a sequence of Int32 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 double Average<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, int> selector
)

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
A sequence of values to calculate the average of.
selector
Type: System.Func<TSource, Int32>
A transform function to apply to each element.

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 IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

OverflowException

The sum of the elements in the sequence is larger than MaxValue.

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<TSource>(IEnumerable<TSource>, Func<TSource, Int32>) to calculate an average.


      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. 



Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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