Artigo
11/18/2011

Enumerable.Sum Method (IEnumerable<Nullable<Int64>>)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Computes the sum of a sequence of nullable Int64 values.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Sum ( _
    source As IEnumerable(Of Nullable(Of Long)) _
) As Nullable(Of Long)

public static Nullable<long> Sum(
    this IEnumerable<Nullable<long>> source
)

Parameters

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

Return Value

Type: System.Nullable<Int64>
The sum of the values in the sequence.

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

Exception	Condition
ArgumentNullException	source is nulla null reference (Nothing in Visual Basic).
OverflowException	The sum is larger than MaxValue.

Remarks

This method returns zero if source contains no elements.

The result does not include values that are nulla null reference (Nothing in Visual Basic).

In Visual Basic query expression syntax, an Aggregate Into Sum() clause translates to an invocation of Sum.

Examples

The following code example demonstrates how to use Sum(IEnumerable<Nullable<Single>>) to sum the values of a sequence.

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.

      ' Create an array of Nullable Single values.
      Dim points() As Nullable(Of Single) = _
          {Nothing, 0, 92.83F, Nothing, 100.0F, 37.46F, 81.1F}

      ' Get the sum of values in the list.
      Dim sum As Nullable(Of Single) = points.Sum()

      ' Display the output.
      outputBlock.Text &= "Total points earned: " & sum & vbCrLf

      ' This code produces the following output:
      '
      ' Total points earned: 311.39

      float?[] points = { null, 0, 92.83F, null, 100.0F, 37.46F, 81.1F };

      float? sum = points.Sum();

      outputBlock.Text += String.Format("Total points earned: {0}", sum) + "\n";

      /*
       This code produces the following output:

       Total points earned: 311.39
      */

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.

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