Measurements.BeforeMeasurement Event

Occurs when a user starts ruler creation.

Namespace: DevExpress.Xpf.Map

Assembly: DevExpress.Xpf.Map.v23.2.dll

NuGet Package: DevExpress.Wpf.Map

Declaration

C#

public event BeforeMeasurementEventHandler BeforeMeasurement

VB.NET

Public Event BeforeMeasurement As BeforeMeasurementEventHandler

Event Data

The BeforeMeasurement event's data class is BeforeMeasurementEventArgs. The following properties provide information specific to this event:

Property	Description
Cancel	Gets or sets a value indicating whether the event should be canceled. Inherited from CancelEventArgs.
RulerAppearance	Specifies ruler appearance settings.
RulerType	Returns the type of the new ruler.
StartPoint	Returns coordinates of the ruler’s start point.

Remarks

The Measurements object raises the BeforeMeasurement event after a user sets the ruler’s first point. To cancel ruler creation, use the e.Cancel property. The e.StartPoint property returns the ruler’s first point. To determine the type of ruler that a user wishes to add, use the e.RulerType property.

The example below cancels ruler creation if a ruler starts inside an ellipse. The MapControl.CalcHitInfo method returns information on the map elements located at the ruler’s first point. The e.StartPoint property returns this point.

C#

private void Measurements_BeforeMeasurement(object sender, BeforeMeasurementEventArgs e) {

 // Convert coordinates to the screen point.
 Point startPoint = mapControl1.CoordPointToScreenPoint(e.StartPoint);

 MapHitInfo info = mapControl1.CalcHitInfo(startPoint);
 if (info.InMapEllipse) {
   e.Cancel = true;
 }
}

VB.NET

Private Sub Measurements_BeforeMeasurement(ByVal sender As Object, ByVal e As BeforeMeasurementEventArgs)

   ' Convert coordinates to the screen point.
   Dim startPoint As Point = mapControl1.CoordPointToScreenPoint(e.StartPoint)
   Dim info As MapHitInfo = mapControl1.CalcHitInfo(startPoint)

   If info.InMapEllipse Then
       e.Cancel = True
   End If
End Sub