项目
11/18/2011

Queryable.Sum Method (IQueryable<Nullable<Decimal>>)

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Computes the sum of a sequence of nullable Decimal values.

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

Syntax

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

public static Nullable<decimal> Sum(
    this IQueryable<Nullable<decimal>> source
)

Parameters

source
Type: System.Linq.IQueryable<Nullable<Decimal>>
A sequence of nullable Decimal values to calculate the sum of.

Return Value

Type: System.Nullable<Decimal>
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 IQueryable<Nullable<Decimal>>. 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

The Sum(IQueryable<Nullable<Decimal>>) method generates a MethodCallExpression that represents calling Sum(IQueryable<Nullable<Decimal>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Sum(IQueryable<Nullable<Decimal>>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the sum of the values in source.

Examples

The following code example demonstrates how to use Sum(IQueryable<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.

      Dim points As Nullable(Of Single)() = {Nothing, 0, 92.83F, Nothing, 100.0F, 37.46F, 81.1F}

      Dim sum As Nullable(Of Single) = points.AsQueryable().Sum()

      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.AsQueryable().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

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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