LiveAggregate<TSource,TAccumulate>(View<TSource>,TAccumulate,Expression<Func<TAccumulate,TSource,TAccumulate>>,Expression<Func<TAccumulate,TSource,TAccumulate>>,Expression<Func<TAccumulate,TSource,Boolean>>) Method

Applies an accumulator function over a view. The specified seed value is used as the initial accumulator value.

Syntax

Visual Basic
C#

'Declaration
 
Public Overloads Shared Function LiveAggregate
    (Of TSource,TAccumulate)( _
   ByVal source As View(Of TSource), _
   ByVal seed As TAccumulate, _
   ByVal funcAdd As System.Linq.Expressions.Expression(Of Func(Of TAccumulate,TSource,TAccumulate)), _
   ByVal funcRemove As System.Linq.Expressions.Expression(Of Func(Of TAccumulate,TSource,TAccumulate)), _
   ByVal funcRemoveDefined As System.Linq.Expressions.Expression(Of Func(Of TAccumulate,TSource,Boolean)) _
) As AggregationView(Of TSource,TAccumulate)

public static AggregationView<TSource,TAccumulate> LiveAggregate<TSource,TAccumulate>( 
   View<TSource> source,
   TAccumulate seed,
   System.Linq.Expressions.Expression<Func<TAccumulate,TSource,TAccumulate>> funcAdd,
   System.Linq.Expressions.Expression<Func<TAccumulate,TSource,TAccumulate>> funcRemove,
   System.Linq.Expressions.Expression<Func<TAccumulate,TSource,bool>> funcRemoveDefined
)

Parameters

source: A view to aggregate over.
seed: The initial accumulator value.
funcAdd: An accumulator function to be invoked on each element that is added to the source view.
funcRemove: A function to be applied to the accumulated value and to an element to obtain the changed accumulated value, when an element is removed from the source view.
funcRemoveDefined: A function used to determine whether funcRemove must be applied when an element is removed from the source view, or the accumulated value is not affected by its removal.

Type Parameters

TSource: The type of the elements of source.
TAccumulate: The type of the accumulator value.

Return Value

A view representing the final accumulator value.

Remarks

It is possible to use standard LINQ query operator Aggregate instead of LiveAggregate. Both are "live" in the sense that they are recomputed automatically when any change occurs in the source. The difference is that Aggregate will every time loop through the entire source collection and aggregate it from scratch, whereas LiveAggregate 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