Average Method (IEnumerable(Nullable(Int64)))

# Enumerable.Average Method (IEnumerable<Nullable<Int64>>)

Computes the average of a sequence of nullable Int64 values.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

## Syntax

```public static Nullable<double> Average(
this IEnumerable<Nullable<long>> source
)
```

#### Parameters

source
Type: System.Collections.Generic.IEnumerable<Nullable<Int64>>
A sequence of nullable Int64 values to calculate the average of.

#### Return Value

Type: System.Nullable<Double>
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<Nullable<Int64>>. When you use instance method syntax to call this method, omit the first parameter.

## Exceptions

ExceptionCondition
ArgumentNullException

source 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 Enumerable.Average.

## Examples

The following code example demonstrates how to use Average(IEnumerable<Nullable<Int64>>) to calculate an average.

```
long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.Average();

outputBlock.Text += String.Format("The average is {0}.", average) + "\n";

// This code produces the following output:
//
// The average is 133282081426.333.

```

## Version Information

#### Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone