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

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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)

Syntax

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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.

Exceptions

Exception	Condition
ArgumentNullException	source or selector is null.
InvalidOperationException	source contains no elements.
OverflowException	The sum of the elements in the sequence is larger than MaxValue.

Remarks

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

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      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.