Imports System.IO
    Imports System.Reflection
    Imports System.Text
    
    Public Class GoogleMapHelper

    ' 1- googlemap_template.html must be copied in the main project folder
    ' 2- add the file into the Visual Studio Solution Explorer (add existing file)
    ' 3- set the properties of the file to: 
    '                                   Build Action -> Embedded Resource
    '                                   Custom Tool Namespace -> write the name of the project

    Private Const ICON_FOLDER As String = "marker_icons/" 'images must be stored in a folder inside  Debug/Release folder
    Private Const MAP_TEMPLATE As String = "WindowsApplication1.googlemap_template.html"
    Private Const TEXT_TO_REPLACE_MARKER_DATA As String = "[[MARKER_DATA]]"
    Private Const TMP_NAME As String = "tmp_map.html"
    

    Private mWebBrowser As WebBrowser

    'MARKER POSITIONS 
    Private mPositions As Double(,) 'lat, lon
    ' marker data allows different formats to include lat,long and optionally title and icon:
    ' op1: mMarkerData = New String(N-1, 1) {{lat1, lon1}, {lat2, lon2}, {latN, lonN}} 
    ' op2: mMarkerData = New String(N-1, 2) {{lat1, lon1,'title1'}, {lat2, lon2,'title2'}, {latN, lonN, 'titleN'}} 
    ' op3: mMarkerData = New String(N-1, 3) {{lat1, lon1,'title1','image1.png'}, {lat2, lon2,'title2','image2.png'}, {latN, lonN, 'titleN','imageN.png'}} 
    Private mMarkerData As String(,) = Nothing
    

    Public Sub New(ByRef wb As WebBrowser, pos As Double(,))
        mWebBrowser = wb
        mPositions = pos
        mMarkerData = getMarkerDataFromPositions(pos)
    End Sub

    Public Sub New(ByRef wb As WebBrowser, md As String(,))
        mWebBrowser = wb
        mMarkerData = md
    End Sub

    Public Sub loadMap()
        mWebBrowser.Navigate(getMapTemplate())
    End Sub

    Private Function getMapTemplate() As String

        If mMarkerData Is Nothing Or mMarkerData.GetLength(1) > 4 Then
            MessageBox.Show("Marker data has not the proper size. It must have 2, 3 o 4 columns")
            Return Nothing
        End If

        Dim htmlTemplate As New StringBuilder()
        Dim tmpFolder As String = Environment.GetEnvironmentVariable("TEMP")
        Dim dataSize As Integer = mMarkerData.GetLength(1) 'number of columns
        Dim mMarkerDataAsText As String = String.Empty
        Dim myresourcePath As String = My.Resources.ResourceManager.BaseName
        Dim myresourcefullPath As String = Path.GetFullPath(My.Resources.ResourceManager.BaseName)
        Dim localPath = myresourcefullPath.Replace(myresourcePath, "").Replace("\", "/") & ICON_FOLDER

        htmlTemplate.AppendLine(getStringFromResources(MAP_TEMPLATE))
        mMarkerDataAsText = "["

        For i As Integer = 0 To mMarkerData.GetLength(0) - 1
            If i <> 0 Then
                mMarkerDataAsText += ","
            End If
            If dataSize = 2 Then 'lat,lon
                mMarkerDataAsText += "[" & mMarkerData(i, 0) & "," + mMarkerData(i, 1) & "]"
            ElseIf dataSize = 3 Then 'lat,lon and title
                mMarkerDataAsText += "[" & mMarkerData(i, 0) & "," + mMarkerData(i, 1) & ",'" & mMarkerData(i, 2) & "']"
            ElseIf dataSize = 4 Then 'lat,lon,title and image
                mMarkerDataAsText += "[" & mMarkerData(i, 0) & "," + mMarkerData(i, 1) & ",'" & mMarkerData(i, 2) & "','" & localPath & mMarkerData(i, 3) & "']" 'Ojo a las comillas simples en las columnas 3 y 4 
            End If
        Next

        mMarkerDataAsText += "]"
        htmlTemplate.Replace(TEXT_TO_REPLACE_MARKER_DATA, mMarkerDataAsText)

        Dim tmpHtmlMapFile As String = (tmpFolder & Convert.ToString("\")) + TMP_NAME
        Dim existsMapFile As Boolean = False
        Try
            existsMapFile = createTxtFile(tmpHtmlMapFile, htmlTemplate)
        Catch ex As Exception
            MessageBox.Show("Error writing temporal file", "Writing Error", MessageBoxButtons.OK, MessageBoxIcon.[Error])
        End Try

        If existsMapFile Then
            Return tmpHtmlMapFile
        Else
            Return Nothing
        End If
    End Function

    Private Function getMarkerDataFromPositions(pos As Double(,)) As String(,)
        Dim md As String(,) = New String(pos.GetLength(0) - 1, 1) {}
        For i As Integer = 0 To pos.GetLength(0) - 1
            md(i, 0) = pos(i, 0).ToString("g", New System.Globalization.CultureInfo("en-US"))
            md(i, 1) = pos(i, 1).ToString("g", New System.Globalization.CultureInfo("en-US"))
        Next
        Return md
    End Function

    Private Function getStringFromResources(resourceName As String) As String
        Dim assem As Assembly = Me.[GetType]().Assembly

        Using stream As Stream = assem.GetManifestResourceStream(resourceName)
            Try
                Using reader As New StreamReader(stream)
                    Return reader.ReadToEnd()
                End Using
            Catch e As Exception
                Throw New Exception((Convert.ToString("Error de acceso al Recurso '") & resourceName) + "'" & vbCr & vbLf + e.ToString())
            End Try
        End Using
    End Function

    Private Function createTxtFile(mFile As String, content As StringBuilder) As Boolean
        Dim mPath As String = Path.GetDirectoryName(mFile)
        If Not Directory.Exists(mPath) Then
            Directory.CreateDirectory(mPath)
        End If
        If File.Exists(mFile) Then
            File.Delete(mFile)
        End If
        Dim sw As StreamWriter = File.CreateText(mFile)
        sw.Write(content.ToString())
        sw.Close()
        Return True
    End Function
    End Class