# Enumerable.Average Method (IEnumerable<Double>)

Silverlight

Computes the average of a sequence of Double values.

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

## Syntax

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

#### Parameters

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

#### 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<Double>. When you use instance method syntax to call this method, omit the first parameter.

## Exceptions

ExceptionCondition
ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

## Remarks

If the sum of the elements is too large to represent as a Double, this method returns positive or negative infinity.

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(IEnumerable<Int32>) 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, substitute the elements of the source sequence with elements of the appropriate numerical type.

```
List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

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

// This code produces the following output:
//
// The average grade is 77.6.

```

## Version Information

#### Silverlight

Supported in: 5, 4, 3

#### Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

#### XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

## Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.