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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

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, 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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
ExceptionCondition
ArgumentNullException

source or selector is null.

InvalidOperationException

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.

NoteNote

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);

            Console.WriteLine("The average string length is {0}.", average);

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



.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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