UsesAllValues プロパティは、このオペランドが条件の評価にコンテキストの AllValues プロパティを使用するかどうかを示します。実際には、値の条件の評価が評価されている値セットの他の値に依存するかどうかを示します。たとえば、データ プレゼンターでは、‘AboveAverage’ 条件は、値が平均以上かどうかを決定する条件になります。フィールドのすべての値を考慮する必要があります。これは、フィールドの値が任意のレコードで変更された時にデータ プレゼンターを示します。すべてのレコードは、フィールドの値の新しい平均値に基づいて正しい結果を反映させるために、条件を再評価します。
注 値セット (平均など) の属性を計算するために AllValues を使用するオペランドなどは、ConditionEvaluationContext.UserCache プロパティを使用して計算済みの値をキャッシュすることが可能です。このプロパティは、値セットで残りの値の評価に設定される値を返します (データ プレゼンターのレコード コレクションのすべてのフィールドの値など)。これによって、同じ値を再計算することを回避できます。呼び出し側は、一度すべての値が評価されると、キャッシュされた値を消去することに注意してください。更に、データが変更されると呼び出し元 (データ プレゼンター) はユーザーのキャッシュを消去するので、データの変更履歴を維持する必要がありません。
Imports Infragistics.Windows Imports Infragistics.Windows.Controls Imports Infragistics.Windows.Editors Imports Infragistics.Windows.DataPresenter Imports Infragistics.Windows.DataPresenter.Events Public Sub New() ' Register the custom operands using SpecialFilterOperands.Register method ' to integrate them with the filtering UI. The data presenter will automatically ' display these operands as options in the filter drop-down of fields with ' matching data type. ' ' Register Odd and then Even operands. SpecialFilterOperands.Register(EvenOrOddOperand.Even) SpecialFilterOperands.Register(EvenOrOddOperand.Odd) InitializeComponent() End Sub ''' <summary> ''' Filter operand used to filter odd or even values. ''' </summary> Public Class EvenOrOddOperand Inherits SpecialFilterOperandBase ' These static instances can be used in XAML to specify initial filters. ' Public Shared ReadOnly Even As EvenOrOddOperand = New EvenOrOddOperand(False) Public Shared ReadOnly Odd As EvenOrOddOperand = New EvenOrOddOperand(True) Private _isOdd As Boolean ''' <summary> ''' Constructor ''' </summary> ''' <param name="isOdd">Whether this instance will filter odd values or even values.</param> Private Sub New(ByVal isOdd As Boolean) _isOdd = isOdd End Sub ' Name of the operand. This is never displayed to the end user. It's a way to ' identify the operand in code. Public Overrides ReadOnly Property Name() As String Get Return IIf(_isOdd, "Odd", "Even") End Get End Property ' Description of the operand. Public Overrides ReadOnly Property Description() As Object Get Return IIf(_isOdd, "Odd values", "Even values") End Get End Property ' The text that gets displayed to represent this operand. Public Overrides ReadOnly Property DisplayContent() As Object Get Return IIf(_isOdd, "Odd", "Even") End Get End Property Public Overrides Function IsMatch(ByVal comparisonOperator As Infragistics.Windows.Controls.ComparisonOperator, ByVal value As Object, ByVal context As Infragistics.Windows.Controls.ConditionEvaluationContext) As Boolean ' This method will only get called for operators that we indicated as supported in ' the SupportsOperator method. If comparisonOperator.Equals = comparisonOperator Then Dim valueAsDouble As Double = context.CurrentValue.ValueAsDouble If Not Double.IsNaN(valueAsDouble) Then If _isOdd Then Return 1 = (CType(valueAsDouble, Integer) Mod 2) Else Return 0 = (CType(valueAsDouble, Integer) Mod 2) End If End If ' If the value is not a valid number (it's null for example), then return false ' since it's neither odd nor even. Return False ElseIf comparisonOperator.NotEquals = comparisonOperator Then ' For NotEquals, simply negate the result of Equals. Return Not Me.IsMatch(comparisonOperator.Equals, value, context) Else Return False End If End Function Public Overrides Function SupportsDataType(ByVal type As System.Type) As Boolean ' This operand supports int and nullable int types. Data presenter will automatically ' show this operand in filter drop-down of fields with int and int? data types. All ' you have to do is register the operand using SpecialFilterOperands.Register as we ' are doing in the InitializeComponent. ' Return type Is GetType(Integer) OrElse type Is GetType(Nullable(Of Integer)) End Function Public Overrides Function SupportsOperator(ByVal comparisonOperator As Infragistics.Windows.Controls.ComparisonOperator) As Boolean ' Only Equals and NotEquals operators make sense for this operand. NotEquals ' is probably not that useful for this operand however for demonstration purposes ' we'll include it here. ' Return comparisonOperator.Equals = comparisonOperator _ OrElse comparisonOperator.NotEquals = comparisonOperator End Function Public Overrides ReadOnly Property UsesAllValues() As Boolean Get ' NOTE: This property is only applicable if you want to create advanced operands that ' rely on data from all records to test a value for match, for example AboveAverage. ' ' UsesAllValues is used to indicate that the operand relies on all the values ' of the records to work. Examples of such operands would be AboveAverage, BelowAverage, ' Top10 etc... With AboveAverage for example, to check if a value is above average, ' we need to calculate the average of all the values. Such an operand would return true ' from this property. It would then use the context.AllValues (context is passed into ' the IsMatch) to calculate the average of all values and check if a particular value ' is above the calculated average. Note that There is a way to cache the calculated ' value via the context.UserCache property - that way the average doesn't have to be ' re-calculated for every value that IsMatch will be called for. The data presenter will ' manage the cache and clear it when cell data changes so all you have to do is check ' if context.UserCache is null and if so recalculate it and cache it again on the ' context.UserCache. ' Return False End Get End Property End Class
using Infragistics.Windows; using Infragistics.Windows.Controls; using Infragistics.Windows.Editors; using Infragistics.Windows.DataPresenter; using Infragistics.Windows.DataPresenter.Events; public Window1( ) { // Register the custom operands using SpecialFilterOperands.Register method // to integrate them with the filtering UI. The data presenter will automatically // display these operands as options in the filter drop-down of fields with // matching data type. // // Register Odd and then Even operands. SpecialFilterOperands.Register( EvenOrOddOperand.Even ); SpecialFilterOperands.Register( EvenOrOddOperand.Odd ); InitializeComponent( ); } /// <summary> /// Filter operand used to filter odd or even values. /// </summary> public class EvenOrOddOperand : SpecialFilterOperandBase { // These static instances can be used in XAML to specify initial filters. // public static readonly EvenOrOddOperand Even = new EvenOrOddOperand( false ); public static readonly EvenOrOddOperand Odd = new EvenOrOddOperand( true ); private bool _isOdd; /// <summary> /// Constructor /// </summary> /// <param name="isOdd">Whether this instance will filter odd values or even values.</param> private EvenOrOddOperand( bool isOdd ) { _isOdd = isOdd; } // Name of the operand. This is never displayed to the end user. It's a way to // identify the operand in code. public override string Name { get { return _isOdd ? "Odd" : "Even"; } } // Description of the operand. public override object Description { get { return _isOdd ? "Odd values" : "Even values"; } } // The text that gets displayed to represent this operand. public override object DisplayContent { get { return _isOdd ? "Odd" : "Even"; } } public override bool IsMatch( ComparisonOperator comparisonOperator, object value, ConditionEvaluationContext context ) { // This method will only get called for operators that we indicated as supported in // the SupportsOperator method. // if ( ComparisonOperator.Equals == comparisonOperator ) { double valueAsDouble = context.CurrentValue.ValueAsDouble; if ( !double.IsNaN( valueAsDouble ) ) { if ( _isOdd ) return 1 == (int)valueAsDouble % 2; else return 0 == (int)valueAsDouble % 2; } // If the value is not a valid number (it's null for example), then return false // since it's neither odd nor even. // return false; } else if ( ComparisonOperator.NotEquals == comparisonOperator ) { // For NotEquals, simply negate the result of Equals. // return !this.IsMatch( ComparisonOperator.Equals, value, context ); } else { return false; } } public override bool SupportsDataType( Type type ) { // This operand supports int and nullable int types. Data presenter will automatically // show this operand in filter drop-down of fields with int and int? data types. All // you have to do is register the operand using SpecialFilterOperands.Register as we // are doing in the InitializeComponent. // return typeof( int ) == type || typeof( int? ) == type; } public override bool SupportsOperator( ComparisonOperator comparisonOperator ) { // Only Equals and NotEquals operators make sense for this operand. NotEquals // is probably not that useful for this operand however for demonstration purposes // we'll include it here. // return ComparisonOperator.Equals == comparisonOperator || ComparisonOperator.NotEquals == comparisonOperator; } public override bool UsesAllValues { get { // NOTE: This property is only applicable if you want to create advanced operands that // rely on data from all records to test a value for match, for example AboveAverage. // // UsesAllValues is used to indicate that the operand relies on all the values // of the records to work. Examples of such operands would be AboveAverage, BelowAverage, // Top10 etc... With AboveAverage for example, to check if a value is above average, // we need to calculate the average of all the values. Such an operand would return true // from this property. It would then use the context.AllValues (context is passed into // the IsMatch) to calculate the average of all values and check if a particular value // is above the calculated average. Note that There is a way to cache the calculated // value via the context.UserCache property - that way the average doesn't have to be // re-calculated for every value that IsMatch will be called for. The data presenter will // manage the cache and clear it when cell data changes so all you have to do is check // if context.UserCache is null and if so recalculate it and cache it again on the // context.UserCache. // return false; } } }