Problem with Mark a Point in Googlemap

See more:

C#

VB

WPF

Google-Maps

hi all
i downloaded WPF Map App
then i added MapImage_MouseLeftButtonUp event for click and Mark a Point
this formula is sequel very good in Zoom '15'
but Not good in Others Zoom
my code is :

Private Sub MapImage_MouseLeftButtonUp(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles MapImage.MouseLeftButtonUp
       If (location IsNot Nothing) Then
           '===========================================
           'Left Or Right
           Dim LRMove As Double = ((((e.GetPosition(MapImage).X) / (MapImage.ActualWidth / 100)) - 50) / 10000) * (2.15 * ((15 - zoom) + 1))
           'MsgBox(LRMove)
           Dim diffLeft As Double
           Dim shiftLeft As Double
           If (lng < 178) Then
               If (zoom = 15) Then
                   lng += LRMove
               ElseIf (zoom > 15) Then
                   diffLeft = zoom - 15
                   shiftLeft = ((15 - diffLeft) * LRMove) / 15
                   lng += shiftLeft
               Else
                   diffLeft = 15 - zoom
                   shiftLeft = ((15 + diffLeft) * LRMove) / 15
                   lng += shiftLeft
               End If
           Else
               lng = -180
           End If
           '===============================================
           'Top or Down
           Dim TDMove As Double = ((((e.GetPosition(MapImage).Y) / (MapImage.ActualHeight / 100)) - 50) / 10000) * (1.5 * ((15 - zoom) + 1))
           Dim diffTop As Double
           Dim shiftTop As Double
           If (lat > -88) Then
               If (zoom = 15) Then
                   lat -= TDMove
               ElseIf (zoom > 15) Then
                   diffTop = zoom - 15
                   shiftTop = ((15 + diffTop) * TDMove) / 15
                   lat += shiftTop
               Else
                   diffTop = 15 - zoom
                   shiftTop = ((15 - diffTop) * TDMove) / 15
                   lat -= shiftTop
               End If
           Else
               lat = -90
           End If
           '===============================================
           'ShowMapUsingLatLng()
           ShowMapUsingLatLng()
           '=====================================================
       End If
   End Sub

and ShowMapUsingLatLng Sub is :

Private Sub ShowMapUsingLatLng()
       Dim bmpImage As New BitmapImage()
       Dim mapURL As String = "http://maps.googleapis.com/maps/api/staticmap?" & _
                   "center=" & lat & "," & lng & "&" & _
                   "size=500x400&markers=size:mid%7Ccolor:red%7C" & _
                    lat & "," & lng & "&zoom=" & zoom & "&maptype=" & mapType & "&sensor=false"
       '===================
       'Set Latitude and Longitude
       LatitudeTxtBlck.Text = lat
       LongitudeTxtBlck.Text = lng
       '===================
       ' My.Computer.FileSystem.WriteAllText("E:\a.txt", mapURL & vbCrLf, True)
       bmpImage.BeginInit()
       bmpImage.UriSource = New Uri(mapURL)
       bmpImage.EndInit()

       MapImage.Source = bmpImage
   End Sub

and WPF Map App Project Address is : WpfMapApp

please help me
thanx