UsesAllValues property indicates whether this operand uses context’s AllValues property to evaluate the condition. In effect, it indicates whether condition evaluation of a value depends on other values in the set of values being evaluated. For example, in data presenter, ‘AboveAverage’ condition would be a condition where to determine whether a value is above the average, all values of the field need to be taken into account. This also indicates to the data presenter that when a field’s value is changed in any record, all records need to reevaluate the condition in order to reflect correct results based on the new average of the field values.
Note that for such operands that use AllValues to calculate an attribute of the set of values (for example, average), you can cache the calculated value using the ConditionEvaluationContext.UserCache property. This property will return the value that it's set to for evaluation of the rest of the values in the set of values (for example, all field values in a record collection in data presenter). This way you can avoid re-calculating the same value again. Note that the caller (data presenter) will clear out the cached value once all the values are evaluated. Also note that when the data changes, the caller (data presenter) will clear the user cache and therefore you don't need to keep track of data changes.
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; } } }
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, 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