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

.NET Framework (current version)

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
)
```

#### Parameters

source
Type:

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:

The average of the sequence of values, or null if the source sequence is empty or contains only values that are null.

#### Type Parameters

TSource

The type of the elements of source.

## Exceptions

Exception Condition
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.

```

## Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1