Average(TSource) Method (IEnumerable(TSource), Func(TSource, Nullable(Decimal)))

# Enumerable.Average<TSource> Method (IEnumerable<TSource>, Func<TSource, Nullable<Decimal>>)

Visual Studio 2008

Computes the average of a sequence of nullable Decimal 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

public static Nullable<decimal> Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, Nullable<decimal>> 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, Nullable<Decimal>>

A transform function to apply to each element.

#### Return Value

Type: System.Nullable<Decimal>
The average of the sequence of values, or null if the source sequence is empty or contains only values that are null.

#### 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).

## Exceptions

ExceptionCondition
ArgumentNullException

source or selector is null.

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, Int64>) to calculate an average.

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, change the body of the selector function.

string[] numbers = { "10007", "37", "299846234235" };

double average = numbers.Average(num => Convert.ToInt64(num));

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

// This code produces the following output:
//
// The average is 99948748093.

## Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

## Version Information

#### .NET Framework

Supported in: 3.5

#### .NET Compact Framework

Supported in: 3.5

#### XNA Framework

Supported in: 3.0