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GeoCoordinateWatcher Class

Supplies location data that is based on latitude and longitude coordinates.

System.Object
  System.Device.Location.GeoCoordinateWatcher

Namespace:  System.Device.Location
Assembly:  System.Device (in System.Device.dll)

'Declaration
Public Class GeoCoordinateWatcher _
	Implements IDisposable, INotifyPropertyChanged, IGeoPositionWatcher(Of GeoCoordinate)

The GeoCoordinateWatcher type exposes the following members.

  NameDescription
Public methodGeoCoordinateWatcherInitializes a new instance of GeoCoordinateWatcher with default accuracy settings.
Public methodGeoCoordinateWatcher(GeoPositionAccuracy)Initializes a new instance of GeoCoordinateWatcher, given an accuracy level.
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  NameDescription
Public propertyDesiredAccuracyThe requested accuracy level for the location data that is provided by the GeoCoordinateWatcher.
Public propertyMovementThresholdThe distance that must be moved, in meters, relative to the coordinate from the last PositionChanged event, before the location provider raises another PositionChanged event.
Public propertyPermissionIndicates whether permission to access location data from location providers has been granted or denied.
Public propertyPositionGets the GeoCoordinate which indicates the current location.
Public propertyStatusGets the current status of the GeoCoordinateWatcher.
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  NameDescription
Public methodDisposeReleases all resources that are used by the current instance of the GeoCoordinateWatcher class.
Protected methodDispose(Boolean)Releases all resources used by the current instance of the GeoCoordinateWatcher class.
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeFrees resources and performs other cleanup operations before the GeoCoordinateWatcher is reclaimed by garbage collection. (Overrides Object.Finalize.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Protected methodOnPositionChangedCalled when a PositionChanged event occurs.
Protected methodOnPositionStatusChangedCalled when a StatusChanged event occurs.
Protected methodOnPropertyChangedCalled when a property of the GeoCoordinateWatcher changes.
Public methodStartInitiate the acquisition of data from the current location provider. This method enables PositionChanged events and allows access to the Position property.
Public methodStart(Boolean)Initiate the acquisition of data from the current location provider. This method enables PositionChanged events and allows access to the Position property.
Public methodStopStops the GeoCoordinateWatcher from providing location data and events.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodTryStartInitiates the acquisition of data from the current location provider. This method returns synchronously.
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  NameDescription
Public eventPositionChangedIndicates that the latitude or longitude of the location data has changed.
Public eventStatusChangedIndicates that the status of the GeoCoordinateWatcher object has changed.
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The GeoCoordinateWatcher class supplies coordinate-based location data from the current location provider. The current location provider is prioritized as the highest on the computer, based on a number of factors, such as the age and accuracy of the data from all providers, the accuracy requested by location applications, and the power consumption and performance impact associated with the location provider. The current location provider might change over time, for instance, when a GPS device loses its satellite signal indoors and a Wi-Fi triangulation provider becomes the most accurate provider on the computer.

To begin accessing location data, create a GeoCoordinateWatcher and call Start or TryStart to initiate the acquisition of data from the current location provider.

The Status property can be checked to determine if data is available. If data is available, you can get the location one time from the Position property, or receive continuous location updates by handling the PositionChanged event.

The Permission, Status, and Position properties support INotifyPropertyChanged, so that an application can data-bind to these properties.

In Windows 7, all the System.Device.Location classes are fully functional if a location provider is installed and able to resolve the computer's location.

NoteNote

On Windows 7 Starter Edition, the only supported location provider is the Default Location Provider in Control Panel, and an add-in must be installed to specify latitude and longitude.

Note   In versions of Windows prior to Windows 7, the following conditions apply:

The following program shows how to create a GeoCoordinateWatcher and start acquiring data by using an initialization timeout. The code then prints the coordinates of the location, if known.


Imports System.Device.Location
Module GetLocationProperty
    Public Sub GetLocationProperty()
        Dim watcher As New System.Device.Location.GeoCoordinateWatcher()
        watcher.TryStart(False, TimeSpan.FromMilliseconds(1000))

        Dim coord As GeoCoordinate = watcher.Position.Location

        If coord.IsUnknown <> True Then
            Console.WriteLine("Lat: {0}, Long: {1}", coord.Latitude, coord.Longitude)
        Else
            Console.WriteLine("Unknown latitude and longitude.")
        End If
    End Sub

    Public Sub Main()
        GetLocationProperty()
        Console.ReadLine()
    End Sub

End Module


The following program shows how to receive continuous location updates by subscribing to PositionChanged events.


Imports System.Device.Location
Module GetLocationEvent
    Public Class CLocation
        Private WithEvents watcher As GeoCoordinateWatcher
        Public Sub GetLocationEvent()
            watcher = New System.Device.Location.GeoCoordinateWatcher()
            AddHandler watcher.PositionChanged, AddressOf watcher_PositionChanged
            Dim started As Boolean = watcher.TryStart(False, TimeSpan.FromMilliseconds(1000))

            If Not started Then
                Console.WriteLine("GeoCoordinateWatcher timed out on start.")
            End If
        End Sub

        Private Sub watcher_PositionChanged(ByVal sender As Object, ByVal e As GeoPositionChangedEventArgs(Of GeoCoordinate))
            PrintPosition(e.Position.Location.Latitude, e.Position.Location.Longitude)
        End Sub

        Private Sub PrintPosition(ByVal Latitude As Double, ByVal Longitude As Double)
            Console.WriteLine("Latitude: {0}, Longitude {1}", Latitude, Longitude)
        End Sub
    End Class


    Public Sub Main()
        Dim myLocation As New CLocation()
        myLocation.GetLocationEvent()
        Console.WriteLine("Enter any key to quit.")
        Console.ReadLine()
    End Sub

End Module


.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

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

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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