ValueChangedEventArgs.OldValue Property

Gets the old value of a property.

Namespace: DevExpress.Xpf.Gauges

Assembly: DevExpress.Xpf.Gauges.v20.1.dll

Declaration

public double OldValue { get; }
Public ReadOnly Property OldValue As Double

Property Value

Type Description
Double

A Double that is the old value.

Remarks

The ValueChangedEventArgs class introduces the OldValue and ValueChangedEventArgs.NewValue properties, which store the old property value and the value that has been assigned to the property.

Examples

In some cases, you need to know whether the current value of an indicator is within a particular range. This example shows how to create a state indicator that changes its color depending on the current range.

First, the Circular gauge is created with three ranges and two empty sections. By default, the gauge's needle doesn't belong to any range, so the state indicator is painted as a gray ellipse.

To solve this task it's necessary to handle the RangeBase.IndicatorEnter and RangeBase.IndicatorLeave events in the following way:

- if a needle 'enters' a range, it is painted with the range color;

- if a needle 'leaves' a range, it is painted in gray.

NOTE

In this example we set the ValueIndicatorBase.IsInteractive property to True, so that you can click on a gauge and manually change the current needle value.

Imports Microsoft.VisualBasic
Imports System.Windows
Imports System.Windows.Media
Imports DevExpress.Xpf.Gauges

Namespace DXGauges_RangeEvents

    Partial Public Class MainWindow
        Inherits Window
        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub GreenRange_IndicatorEnter(ByVal sender As Object, ByVal e As IndicatorEnterEventArgs)
            stateIndicator.Fill = New SolidColorBrush(Colors.Green)
        End Sub

        Private Sub GreenRange_IndicatorLeave(ByVal sender As Object, ByVal e As IndicatorLeaveEventArgs)
            stateIndicator.Fill = New SolidColorBrush(Colors.Gray)
        End Sub

        Private Sub YellowRange_IndicatorEnter(ByVal sender As Object, ByVal e As IndicatorEnterEventArgs)
            stateIndicator.Fill = New SolidColorBrush(Colors.Yellow)
        End Sub

        Private Sub YellowRange_IndicatorLeave(ByVal sender As Object, ByVal e As IndicatorLeaveEventArgs)
            If ((e.NewValue) < 10) OrElse (((e.NewValue) > 90)) Then
                stateIndicator.Fill = New SolidColorBrush(Colors.Gray)
            End If
        End Sub

        Private Sub RedRange_IndicatorEnter(ByVal sender As Object, ByVal e As IndicatorEnterEventArgs)
            stateIndicator.Fill = New SolidColorBrush(Colors.Red)
        End Sub

        Private Sub RedRange_IndicatorLeave(ByVal sender As Object, ByVal e As IndicatorLeaveEventArgs)
            If ((e.NewValue) < 10) OrElse (((e.NewValue) > 90)) Then
                stateIndicator.Fill = New SolidColorBrush(Colors.Gray)
            End If
        End Sub
    End Class
End Namespace
See Also