LiveSum<TSource>(View<TSource>,Expression<Func<TSource,Nullable<Int32>>>) Method

Computes the sum of a view of nullable System.Int32 values that are obtained by invoking a transform function on each element of the source view.

Syntax

Visual Basic
C#

'Declaration
 
Public Overloads Shared Function LiveSum(Of TSource)( _
   ByVal source As View(Of TSource), _
   ByVal selector As System.Linq.Expressions.Expression(Of Func(Of TSource,Nullable(Of Integer))) _
) As AggregationView(Of TSource,Nullable(Of Integer))

public static AggregationView<TSource,Nullable<int>> LiveSum<TSource>( 
   View<TSource> source,
   System.Linq.Expressions.Expression<Func<TSource,Nullable<int>>> selector
)

Parameters

source: A view containing the values to calculate the sum of.
selector: A transform function to apply to each element.

Type Parameters

TSource: The type of the elements of source.

Return Value

A view representing the sum of the values.

Remarks

If the source is empty or contains only nulls, the sum value is zero.

It is possible to use standard LINQ query operator Sum instead of LiveSum. Both are "live" in the sense that they are recomputed automatically when any change occurs in the source. The difference is that Sum will every time loop through the entire source collection and aggregate it from scratch, whereas LiveSum will use a more performant algorithm, will maintain its value incrementally, processing only those source items that actually changed.

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

LiveViewExtensions Class
LiveViewExtensions Members
Overload List