' Copyright 2012 ESRI
' 
' All rights reserved under the copyright laws of the United States
' and applicable international laws, treaties, and conventions.
' 
' You may freely redistribute and use this sample code, with or
' without modification, provided you include the original copyright
' notice and use restrictions.
' 
' See the use restrictions.
' 

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections
Imports System.Data
Imports System.Runtime.InteropServices
Imports System.Xml
Imports System.Threading
Imports System.Timers
Imports System.Text.RegularExpressions
Imports System.IO
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Windows.Forms
Imports System.ComponentModel
Imports Microsoft.Win32
Imports ESRI.ArcGIS.ADF.BaseClasses
Imports ESRI.ArcGIS.Carto
Imports ESRI.ArcGIS.Geodatabase
Imports ESRI.ArcGIS.esriSystem
Imports ESRI.ArcGIS.Geometry
Imports ESRI.ArcGIS.Display
Imports ESRI.ArcGIS.DataSourcesFile

  #Region "WeatherItemEventArgs class members"
  Public NotInheritable Class WeatherItemEventArgs : Inherits EventArgs
    Private m_id As Integer
    Private m_zipCode As Long
    Private m_x As Double
    Private m_y As Double
    Private m_iconWidth As Integer
    Private m_iconHeight As Integer

  Public Sub New(ByVal newID As Integer, ByVal newZipCode As Long, ByVal X As Double, ByVal Y As Double, ByVal newIconWidth As Integer, ByVal newIconHeight As Integer)
      m_id = newID
      m_zipCode = newZipCode
      m_x = X
      m_y = Y
      m_iconWidth = newIconWidth
      m_iconHeight = newIconHeight
  End Sub

    Public ReadOnly Property ID() As Integer
      Get
        Return m_id
      End Get
    End Property
    Public ReadOnly Property ZipCode() As Long
      Get
        Return m_zipCode
      End Get
    End Property
    Public ReadOnly Property mapY() As Double
      Get
        Return m_y
      End Get
    End Property
    Public ReadOnly Property mapX() As Double
      Get
        Return m_x
      End Get
    End Property
    Public ReadOnly Property IconWidth() As Integer
      Get
        Return m_iconWidth
      End Get
    End Property
    Public ReadOnly Property IconHeight() As Integer
      Get
        Return m_iconHeight
      End Get
    End Property
  End Class
  #End Region

  'declare delegates for the event handling
  Public Delegate Sub WeatherItemAdded(ByVal sender As Object, ByVal args As WeatherItemEventArgs)
  Public Delegate Sub WeatherItemsUpdated(ByVal sender As Object, ByVal args As EventArgs)


  ''' <summary>
  ''' RSSWeatherLayerClass is a custom layer for ArcMap/MapControl. It inherits CustomLayerBase
  ''' which implements the relevant interfaces required by the Map.
  ''' This sample is a comprehensive sample of a real life scenario for creating a new layer in 
  ''' order to consume a web service and display the information in a map.
  ''' In this sample you can find implementation of simple editing capabilities, selection by 
  ''' attribute and by location, persistence and identify.
  ''' </summary>
  <Guid("3460FB55-4326-4d28-9F96-D62211B0C754"), ClassInterface(ClassInterfaceType.None), ComVisible(True), ProgId("RSSWeatherLayerClass")> _
  Public NotInheritable Class RSSWeatherLayerClass : Inherits BaseDynamicLayer : Implements IIdentify
  #Region "class members"

  Private m_timer As System.Timers.Timer = Nothing
  Private m_updateThread As Thread = Nothing
  Private m_iconFolder As String = String.Empty
  Private m_table As DataTable = Nothing
  Private m_symbolTable As DataTable = Nothing
  Private m_locations As DataTable = Nothing
  Private m_selectionSymbol As ISymbol = Nothing
  Private m_display As IDisplay = Nothing
  Private m_dataFolder As String = String.Empty
  Private m_layerSRFactoryCode As Integer = 0
  Private m_symbolSize As Integer = 32

  Private m_point As IPoint = Nothing
  Private m_llPnt As IPoint = Nothing
  Private m_urPnt As IPoint = Nothing
  Private m_env As IEnvelope = Nothing

  ' dynamic display members
  Private m_dynamicGlyphFactory As IDynamicGlyphFactory2 = Nothing
  Private m_dynamicSymbolProperties As IDynamicSymbolProperties2 = Nothing
  Private m_dynamicCompoundMarker As IDynamicCompoundMarker2 = Nothing
  Private m_textGlyph As IDynamicGlyph = Nothing
  Private m_selectionGlyph As IDynamicGlyph = Nothing
  Private m_bDDOnce As Boolean = True

  'weather items events
  Public Event OnWeatherItemAdded As WeatherItemAdded
  Public Event OnWeatherItemsUpdated As WeatherItemsUpdated
  #End Region

  #Region "Constructor"
  ''' <summary>
  ''' The class has only default CTor.
  ''' </summary>
  Public Sub New()
    MyBase.New()
    Try
      'set the layer's name
      MyBase.m_sName = "RSS Weather Layer"
      'ask the Map to create a separate cache for the layer
      MyBase.m_IsCached = False

      ' the underlying data for this layer is always in WGS1984 geographical coordinate system
      m_spatialRef = CreateGeographicSpatialReference()
      m_layerSRFactoryCode = m_spatialRef.FactoryCode

      'get the directory for the layer's cache. If it does not exist, create it.
      m_dataFolder = System.IO.Path.Combine(System.IO.Path.GetTempPath(), "RSSWeatherLayer")
      If (Not System.IO.Directory.Exists(m_dataFolder)) Then
        System.IO.Directory.CreateDirectory(m_dataFolder)
      End If
      m_iconFolder = m_dataFolder

      'instantiate the timer for the weather update
      m_timer = New System.Timers.Timer(1000)
      m_timer.Enabled = False
      AddHandler m_timer.Elapsed, AddressOf OnUpdateTimer

      'initialize the layer's tables (main table as well as the symbols table)
      InitializeTables()

      'get the location list from a featureclass (US major cities) and synchronize it with the 
      'cached information in case it exists.
      If Nothing Is m_locations Then
        InitializeLocations()
      End If

      'initialize the selection symbol used to highlight selected weather items
      InitializeSelectionSymbol()

      m_point = New PointClass()
      m_llPnt = New PointClass()
      m_urPnt = New PointClass()
      m_env = New EnvelopeClass()

      'connect to the RSS service
      Connect()
      Catch ex As Exception
        System.Diagnostics.Trace.WriteLine(ex.Message)
      End Try
  End Sub

  Protected Overrides Sub Finalize()
    Disconnect()
  End Sub
  #End Region

#Region "Overridden methods"

    ''' <summary>
    ''' Draws the layer to the specified display for the given draw phase. 
    ''' </summary>
    ''' <param name="drawPhase"></param>
    ''' <param name="Display"></param>
    ''' <param name="trackCancel"></param>
    ''' <remarks>the draw method is set as an abstract method and therefore must be overridden</remarks>
    Public Overrides Sub Draw(ByVal drawPhase As esriDrawPhase, ByVal Display As IDisplay, ByVal trackCancel As ITrackCancel)
        If drawPhase <> esriDrawPhase.esriDPGeography Then
            Return
        End If
        If Display Is Nothing Then
            Return
        End If
        If m_table Is Nothing OrElse m_symbolTable Is Nothing Then
            Return
        End If

        m_display = Display

        Dim envelope As IEnvelope = TryCast(Display.DisplayTransformation.FittedBounds, IEnvelope)

        Dim lat, lon As Double
        Dim iconCode As Integer
        Dim selected As Boolean
        Dim symbol As ISymbol = Nothing

        'loop through the rows. Draw each row that has a shape
        For Each row As DataRow In m_table.Rows
            'get the Lat/Lon of the item
            lat = Convert.ToDouble(row(3))
            lon = Convert.ToDouble(row(4))
            'get the icon ID
            iconCode = Convert.ToInt32(row(8))

            'get the selection state of the item
            selected = Convert.ToBoolean(row(13))

            If lon >= envelope.XMin AndAlso lon <= envelope.XMax AndAlso lat >= envelope.YMin AndAlso lat <= envelope.YMax Then
                'search for the symbol in the symbology table
                symbol = GetSymbol(iconCode, row)
                If Nothing Is symbol Then
                    Continue For
                End If

                m_point.X = lon
                m_point.Y = lat
                m_point.SpatialReference = m_spatialRef

                'reproject the point to the DataFrame's spatial reference
                If Not Nothing Is m_mapSpatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode Then
                    m_point.Project(m_mapSpatialRef)
                End If

                Display.SetSymbol(symbol)
                Display.DrawPoint(m_point)

                If selected Then
                    Display.SetSymbol(m_selectionSymbol)
                    Display.DrawPoint(m_point)
                End If
            End If
        Next row
    End Sub

    ''' <summary>
    ''' Draw the layer while in dynamic mode
    ''' </summary>
    ''' <param name="DynamicDrawPhase"></param>
    ''' <param name="Display"></param>
    ''' <param name="DynamicDisplay"></param>
    Public Overrides Sub DrawDynamicLayer(ByVal DynamicDrawPhase As esriDynamicDrawPhase, ByVal Display As IDisplay, ByVal DynamicDisplay As IDynamicDisplay)
        If DynamicDrawPhase <> esriDynamicDrawPhase.esriDDPCompiled Then
            Return
        End If

        If (Not m_bValid) OrElse (Not m_visible) Then
            Return
        End If

        If m_bDDOnce Then
            m_dynamicGlyphFactory = TryCast(DynamicDisplay.DynamicGlyphFactory, IDynamicGlyphFactory2)
            m_dynamicSymbolProperties = TryCast(DynamicDisplay, IDynamicSymbolProperties2)
            m_dynamicCompoundMarker = TryCast(DynamicDisplay, IDynamicCompoundMarker2)

            m_textGlyph = m_dynamicGlyphFactory.DynamicGlyph(1, esriDynamicGlyphType.esriDGlyphText, 1)

            ' create glyph for the selection symbol
            If m_selectionSymbol Is Nothing Then
                InitializeSelectionSymbol()
            End If

            m_selectionGlyph = m_dynamicGlyphFactory.CreateDynamicGlyph(m_selectionSymbol)

            m_bDDOnce = False
        End If

        m_display = Display

        Dim lat, lon As Double
        Dim iconCode As Integer
        Dim iconWidth As Integer = 0
        Dim selected As Boolean
        Dim dynamicGlyph As IDynamicGlyph = Nothing
        Dim symbolSized As Single
        Dim citiName As String = String.Empty
        Dim temperature As String = String.Empty

        'loop through the rows. Draw each row that has a shape
        For Each row As DataRow In m_table.Rows
            'get the Lat/Lon of the item
            lat = Convert.ToDouble(row(3))
            lon = Convert.ToDouble(row(4))
            'get the icon ID
            iconCode = Convert.ToInt32(row(8))

            ' get citiname and temperature
            citiName = Convert.ToString(row(2))
            temperature = String.Format("{0} F", row(5))

            'get the selection state of the item
            selected = Convert.ToBoolean(row(13))

            'search for the symbol in the symbology table
            dynamicGlyph = GetDynamicGlyph(m_dynamicGlyphFactory, iconCode, row, iconWidth)
            If Nothing Is dynamicGlyph Then
                Continue For
            End If

            m_point.X = lon
            m_point.Y = lat
            m_point.SpatialReference = m_spatialRef

            'reproject the point to the DataFrame's spatial reference
            If Not Nothing Is m_spatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode Then
                m_point.Project(m_mapSpatialRef)
            End If

            symbolSized = 1.35F * CSng(m_symbolSize / CDbl(iconWidth))

            ' draw the weather item

            ' 1. set the whether symbol properties
            m_dynamicSymbolProperties.DynamicGlyph(esriDynamicSymbolType.esriDSymbolMarker) = dynamicGlyph
            m_dynamicSymbolProperties.RotationAlignment(esriDynamicSymbolType.esriDSymbolMarker) = esriDynamicSymbolRotationAlignment.esriDSRAScreen
            m_dynamicSymbolProperties.Heading(esriDynamicSymbolType.esriDSymbolMarker) = 0.0F
            m_dynamicSymbolProperties.SetColor(esriDynamicSymbolType.esriDSymbolMarker, 1.0F, 1.0F, 1.0F, 1.0F)
            m_dynamicSymbolProperties.SetScale(esriDynamicSymbolType.esriDSymbolMarker, symbolSized, symbolSized)
            m_dynamicSymbolProperties.Smooth(esriDynamicSymbolType.esriDSymbolMarker) = False

            ' 2. set the text properties
            m_dynamicSymbolProperties.DynamicGlyph(esriDynamicSymbolType.esriDSymbolText) = m_textGlyph
            m_dynamicSymbolProperties.RotationAlignment(esriDynamicSymbolType.esriDSymbolMarker) = esriDynamicSymbolRotationAlignment.esriDSRAScreen
            m_dynamicSymbolProperties.Heading(esriDynamicSymbolType.esriDSymbolText) = 0.0F
            m_dynamicSymbolProperties.SetColor(esriDynamicSymbolType.esriDSymbolText, 0.0F, 0.85F, 0.0F, 1.0F)
            m_dynamicSymbolProperties.SetScale(esriDynamicSymbolType.esriDSymbolText, 1.0F, 1.0F)
            m_dynamicSymbolProperties.Smooth(esriDynamicSymbolType.esriDSymbolText) = False
            m_dynamicSymbolProperties.TextBoxUseDynamicFillSymbol = False
            m_dynamicSymbolProperties.TextBoxHorizontalAlignment = esriTextHorizontalAlignment.esriTHACenter
            m_dynamicSymbolProperties.TextRightToLeft = False

            ' draw both the icon and the text as a compound marker
            m_dynamicCompoundMarker.DrawCompoundMarker2(m_point, temperature, citiName)

            If selected Then ' draw the selected symbol
                m_dynamicSymbolProperties.SetColor(esriDynamicSymbolType.esriDSymbolMarker, 0.0F, 1.0F, 1.0F, 1.0F)
                m_dynamicSymbolProperties.DynamicGlyph(esriDynamicSymbolType.esriDSymbolMarker) = m_selectionGlyph
                DynamicDisplay.DrawMarker(m_point)
            End If
        Next row

        MyBase.m_bIsCompiledDirty = False
    End Sub

    ''' <summary>
    ''' The spatial reference of the underlying data.
    ''' </summary>
    Public Overrides ReadOnly Property SpatialReference() As ISpatialReference
        Get
            If Nothing Is m_spatialRef Then
                m_spatialRef = CreateGeographicSpatialReference()
            End If
            Return m_spatialRef
        End Get
    End Property

    ''' <summary>
    ''' The ID of the object. 
    ''' </summary>
    Public Overrides ReadOnly Property ID() As ESRI.ArcGIS.esriSystem.UID
        Get
            Dim uid As UID = New UIDClass()
            uid.Value = "RSSWeatherLayerClass"

            Return uid
        End Get
    End Property

    ''' <summary>
    ''' The default area of interest for the layer. Returns the spatial-referenced extent of the layer. 
    ''' </summary>
    Public Overrides ReadOnly Property AreaOfInterest() As IEnvelope
        Get
            Return Me.Extent
        End Get
    End Property

    ''' <summary>
    ''' The layer's extent which is a union of the extents of all the items of the layer 
    ''' </summary>
    ''' <remarks>In case where the DataFram's spatial reference is different than the underlying
    ''' data's spatial reference the envelope must be projected</remarks>
    Public Overrides ReadOnly Property Extent() As IEnvelope
        Get
            m_extent = GetLayerExtent()
            If Nothing Is m_extent Then
                Return Nothing
            End If

            Dim env As IEnvelope = TryCast((CType(m_extent, IClone)).Clone(), IEnvelope)
            If Not Nothing Is m_mapSpatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode Then
                env.Project(m_mapSpatialRef)
            End If

            Return env
        End Get
    End Property

    ''' <summary>
    ''' Map tip text at the specified mouse location.
    ''' </summary>
    ''' <param name="X"></param>
    ''' <param name="Y"></param>
    ''' <param name="Tolerance"></param>
    ''' <returns></returns>
    Public Overrides Function get_TipText(ByVal X As Double, ByVal Y As Double, ByVal Tolerance As Double) As String
        Dim envelope As IEnvelope = New EnvelopeClass()
        envelope.PutCoords(X - Tolerance, Y - Tolerance, X + Tolerance, Y + Tolerance)

        'reproject the envelope to the datasource coordinate system
        If Not Nothing Is m_mapSpatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode Then
            envelope.SpatialReference = m_spatialRef
            envelope.Project(m_mapSpatialRef)
        End If

        Dim xmin, ymin, xmax, ymax As Double
        envelope.QueryCoords(xmin, ymin, xmax, ymax)

        'select all the records within the given extent
        Dim qry As String = "LON >= " & xmin.ToString() & " AND LON <= " & xmax.ToString() & " AND Lat >= " & ymin.ToString() & " AND LAT <= " & ymax.ToString()
        Dim rows As DataRow() = m_table.Select(qry)
        If 0 = rows.Length Then
            Return String.Empty
        End If

        Dim r As DataRow = rows(0)
        Dim zipCode As String = Convert.ToString(r(1))
        Dim cityName As String = Convert.ToString(r(2))
        Dim temperature As String = Convert.ToString(r(5))

        Return cityName & ", " & zipCode & ", " & temperature & "F"
    End Function

#End Region

  #Region "public methods"

  ''' <summary>
  ''' connects to RSS weather service
  ''' </summary>
    Public Sub Connect()
    'enable the update timer
      m_timer.Enabled = True

      MyBase.m_bIsCompiledDirty = True
    End Sub

  ''' <summary>
  ''' disconnects from RSS weather service
  ''' </summary>
    Public Sub Disconnect()
    'disable the update timer
    m_timer.Enabled = False

      Try
    'abort the update thread in case that it is alive
        If m_updateThread.IsAlive Then
          m_updateThread.Abort()
        End If
      Catch
        System.Diagnostics.Trace.WriteLine("WeatherLayer update thread has been terminated")
      End Try
    End Sub

  ''' <summary>
  ''' select a weather item by its zipCode
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <param name="newSelection"></param>
    Public Sub [Select](ByVal zipCode As Long, ByVal newSelection As Boolean)
      If Nothing Is m_table Then
        Return
      End If

      If newSelection Then
        UnselectAll()
      End If

      Dim rows As DataRow() = m_table.Select("ZIPCODE = " & zipCode.ToString())
      If rows.Length = 0 Then
        Return
      End If

      Dim rec As DataRow = rows(0)
      SyncLock m_table
        '13 is the selection column ID
        rec(13) = True
        rec.AcceptChanges()
      End SyncLock
      MyBase.m_bIsCompiledDirty = True
    End Sub

  ''' <summary>
  ''' unselect all weather items
  ''' </summary>
    Public Sub UnselectAll()
      If Nothing Is m_table Then
        Return
      End If

      'unselect all the currently selected items
      SyncLock m_table
        For Each r As DataRow In m_table.Rows
          '13 is the selection column ID
          r(13) = False
        Next r
        m_table.AcceptChanges()
      End SyncLock

      MyBase.m_bIsCompiledDirty = True
    End Sub

  ''' <summary>
  ''' Run the update thread
  ''' </summary>
  ''' <remarks>calling this method to frequently might end up in blockage of RSS service.
  ''' The service will interpret the excessive calls as an offence and thus would block the service for a while.</remarks>
    Public Sub Refresh()
      Try
        m_updateThread = New Thread(AddressOf ThreadProc)

        'run the update thread
        m_updateThread.Start()
      Catch ex As Exception
        System.Diagnostics.Trace.WriteLine(ex.Message)
      End Try
    End Sub

  ''' <summary>
  ''' add a new item given only a zipcode (will use the default location given by the service)
  ''' should the item exists, it will get updated
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <returns></returns>
    Public Function AddItem(ByVal zipCode As Long) As Boolean
      Return AddItem(zipCode, 0.0,0.0)
    End Function

  ''' <summary>
  ''' adds a new item given a zipcode and a coordinate.
  ''' Should the item already exists, it will get updated and will move to the new coordinate.
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <param name="lat"></param>
  ''' <param name="lon"></param>
  ''' <returns></returns>
    Public Function AddItem(ByVal zipCode As Long, ByVal lat As Double, ByVal lon As Double) As Boolean
      If Nothing Is m_table Then
        Return False
      End If

      Dim r As DataRow = m_table.Rows.Find(zipCode)
      If Not Nothing Is r Then 'if the record with this zipCode already exists
        'in case that the record exists and the input coordinates are not valid 
        If lat = 0.0 AndAlso lon = 0.0 Then
          Return False
        Else 'update the location according to the new coordinate
          SyncLock m_table
            r(3) = lat
            r(4) = lon

            r.AcceptChanges()
          End SyncLock
        End If
      Else
        'add new zip code to the locations list
        Dim rec As DataRow = m_locations.NewRow()
        SyncLock m_locations
          rec(1) = zipCode
          m_locations.Rows.Add(rec)
        End SyncLock

        'need to connect to the service and get the info
        AddWeatherItem(zipCode, lat, lon)
      End If

      Return True
    End Function

  ''' <summary>
  ''' delete an item from the dataset
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <returns></returns>
    Public Function DeleteItem(ByVal zipCode As Long) As Boolean
      If Nothing Is m_table Then
        Return False
      End If

      Try
        Dim r As DataRow = m_table.Rows.Find(zipCode)
        If Not Nothing Is r Then 'if the record with this zipCode already exists
          SyncLock m_table
            r.Delete()
          End SyncLock
          MyBase.m_bIsCompiledDirty = True
          Return True
        End If
        MyBase.m_bIsCompiledDirty = True
        Return False
      Catch ex As Exception
        System.Diagnostics.Trace.WriteLine(ex.Message)
        Return False
      End Try
    End Function

  ''' <summary>
  ''' get a weather item given a city name.
  ''' </summary>
  ''' <param name="cityName"></param>
  ''' <returns></returns>
  ''' <remarks>a city might have more than one zipCode and therefore this method will
  ''' return the first zipcOde found for the specified city name.</remarks>
    Public Function GetWeatherItem(ByVal cityName As String) As IPropertySet
      If Nothing Is m_table Then
        Return Nothing
      End If

      Dim rows As DataRow() = m_table.Select("CITYNAME = '" & cityName & "'")
      If rows.Length = 0 Then
        Return Nothing
      End If

      Dim zipCode As Long = Convert.ToInt64(rows(0)(1))
      Return GetWeatherItem(zipCode)
    End Function

  ''' <summary>
  ''' This method searches for the record of the given zipcode and retunes the information as a PropertySet.
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <returns>a PropertySet encapsulating the weather information for the given weather item.</returns>
    Public Function GetWeatherItem(ByVal zipCode As Long) As IPropertySet
      Dim r As DataRow = m_table.Rows.Find(zipCode)
      If Nothing Is r Then
        Return Nothing
      End If

      Dim propSet As IPropertySet = New PropertySetClass()
      propSet.SetProperty("ID", r(0))
      propSet.SetProperty("ZIPCODE", r(1))
      propSet.SetProperty("CITYNAME", r(2))
      propSet.SetProperty("LAT", r(3))
      propSet.SetProperty("LON", r(4))
      propSet.SetProperty("TEMPERATURE", r(5))
      propSet.SetProperty("CONDITION", r(6))
      propSet.SetProperty("ICONNAME", r(7))
      propSet.SetProperty("ICONID", r(8))
      propSet.SetProperty("DAY", r(9))
      propSet.SetProperty("DATE", r(10))
      propSet.SetProperty("LOW", r(11))
      propSet.SetProperty("HIGH", r(12))
      propSet.SetProperty("UPDATEDATE", r(14))

      Return propSet
    End Function

  ''' <summary>
  ''' get a list of all citynames currently in the dataset.
  ''' </summary>
  ''' <returns></returns>
  ''' <remarks>Please note that since the unique ID is zipCode, it is possible
  ''' to have a city name appearing more than once.</remarks>
    Public Function GetCityNames() As String()
      If Nothing Is m_table OrElse 0 = m_table.Rows.Count Then
        Return Nothing
      End If

      Dim cityNames As String() = New String(m_table.Rows.Count - 1){}
      Dim i As Integer=0
      Do While i<m_table.Rows.Count
        'column #2 stores the cityName
        cityNames(i) = Convert.ToString(m_table.Rows(i)(2))
        i += 1
      Loop

      Return cityNames
    End Function

  ''' <summary>
  ''' Zoom to a weather item according to its city name
  ''' </summary>
  ''' <param name="cityName"></param>
  Public Sub ZoomTo(ByVal cityName As String)
    If Nothing Is m_table Then
      Return
    End If

    Dim rows As DataRow() = m_table.Select("CITYNAME = '" & cityName & "'")
    If rows.Length = 0 Then
      Return
    End If

    Dim zipCode As Long = Convert.ToInt64(rows(0)(1))
    ZoomTo(zipCode)
  End Sub

  ''' <summary>
  ''' Zoom to weather item according to its zipcode
  ''' </summary>
  ''' <param name="zipCode"></param>
  Public Sub ZoomTo(ByVal zipCode As Long)
    If Nothing Is m_table OrElse Nothing Is m_symbolTable Then
      Return
    End If

    If Nothing Is m_display Then
      Return
    End If

    'get the record for the requested zipCode
    Dim r As DataRow = m_table.Rows.Find(zipCode)
    If Nothing Is r Then
      Return
    End If

    'get the coordinate of the zipCode
    Dim lat As Double = Convert.ToDouble(r(3))
    Dim lon As Double = Convert.ToDouble(r(4))

    Dim point As IPoint = New PointClass()
    point.X = lon
    point.Y = lat
    point.SpatialReference = m_spatialRef

    If Not Nothing Is m_mapSpatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode Then
      point.Project(m_mapSpatialRef)
    End If

    Dim iconCode As Integer = Convert.ToInt32(r(8))
        'find the appropriate symbol record
    Dim rec As DataRow = m_symbolTable.Rows.Find(iconCode)
    If rec Is Nothing Then
      Return
    End If

    'get the icon's dimensions
    Dim iconWidth As Integer = Convert.ToInt32(rec(3))
    Dim iconHeight As Integer = Convert.ToInt32(rec(4))

    Dim displayTransformation As IDisplayTransformation = (CType(m_display, IScreenDisplay)).DisplayTransformation

    'Convert the icon coordinate into screen coordinate
    Dim windowX, windowY As Integer
    displayTransformation.FromMapPoint(point,windowX, windowY)

    'get the upper left coord
    Dim ulx, uly As Integer
    ulx = Convert.ToInt32(windowX - iconWidth / 2)
    uly = Convert.ToInt32(windowY - iconHeight / 2)
    Dim ulPnt As IPoint = displayTransformation.ToMapPoint(ulx, uly)

    'get the lower right coord
    Dim lrx, lry As Integer
    lrx = Convert.ToInt32(windowX + iconWidth / 2)
    lry = Convert.ToInt32(windowY + iconHeight / 2)
    Dim lrPnt As IPoint = displayTransformation.ToMapPoint(lrx, lry)

    'construct the new extent
    Dim envelope As IEnvelope = New EnvelopeClass()
    envelope.PutCoords(ulPnt.X, lrPnt.Y, lrPnt.X, ulPnt.Y)
    envelope.Expand(2,2,False)

    'set the new extent and refresh the display
    displayTransformation.VisibleBounds = envelope

    MyBase.m_bIsCompiledDirty = True

    CType(m_display, IScreenDisplay).Invalidate(Nothing, True, CShort(esriScreenCache.esriAllScreenCaches))
    CType(m_display, IScreenDisplay).UpdateWindow()
  End Sub

  Private Sub SetSymbolSize(ByVal newSize As Integer)
    If newSize <= 0 Then
      MessageBox.Show("Size is not allowed.")
      Return
    End If

    m_symbolSize = newSize

    If Nothing Is m_symbolTable OrElse 0 = m_symbolTable.Rows.Count Then
      Return
    End If

    Dim pictureMarkerSymbol As IPictureMarkerSymbol = Nothing

    SyncLock m_symbolTable
    For Each r As DataRow In m_symbolTable.Rows
      pictureMarkerSymbol = TryCast(r(2), IPictureMarkerSymbol)
      If Nothing Is pictureMarkerSymbol Then
        Continue For
      End If

      pictureMarkerSymbol.Size = newSize
      r(2) = pictureMarkerSymbol
      r.AcceptChanges()
    Next r
    End SyncLock

    MyBase.m_bIsCompiledDirty = True

    CType(m_display, IScreenDisplay).Invalidate(Nothing, True, CShort(esriScreenCache.esriAllScreenCaches))
    CType(m_display, IScreenDisplay).UpdateWindow()
  End Sub

  Public Property SymbolSize() As Integer
    Set
      SetSymbolSize(Value)
    End Set
    Get
      Return m_symbolSize
    End Get
  End Property

    #End Region

    #Region "private utility methods"

  ''' <summary>
  ''' create a WGS1984 geographic coordinate system.
  ''' In this case, the underlying data provided by the service is in WGS1984.
  ''' </summary>
  ''' <returns></returns>
    Private Function CreateGeographicSpatialReference() As ISpatialReference
      Dim spatialRefFatcory As ISpatialReferenceFactory = New SpatialReferenceEnvironmentClass()
      Dim geoCoordSys As IGeographicCoordinateSystem
      geoCoordSys = spatialRefFatcory.CreateGeographicCoordinateSystem(CInt(esriSRGeoCSType.esriSRGeoCS_WGS1984))
      geoCoordSys.SetFalseOriginAndUnits(-180.0, -180.0, 5000000.0)
      geoCoordSys.SetZFalseOriginAndUnits(0.0, 100000.0)
      geoCoordSys.SetMFalseOriginAndUnits(0.0, 100000.0)

      Return TryCast(geoCoordSys, ISpatialReference)
    End Function

  ''' <summary>
  ''' get the overall extent of the items in the layer
  ''' </summary>
  ''' <returns></returns>
    Private Function GetLayerExtent() As IEnvelope
    'iterate through all the items in the layers DB and get the bounding envelope
      Dim env As IEnvelope = New EnvelopeClass()
      env.SpatialReference = m_spatialRef
      Dim point As IPoint = New PointClass()
      point.SpatialReference = m_spatialRef
      Dim symbolCode As Integer = 0
      Dim newSymbolSize As Double = 0
      For Each r As DataRow In m_table.Rows
        If TypeOf r(3) Is DBNull OrElse TypeOf r(4) Is DBNull Then
          Continue For
        End If

        point.Y = Convert.ToDouble(r(3))
        point.X = Convert.ToDouble(r(4))

        ' need to get the symbol size in meters in order to add it to the total layer extent
        If Not m_display Is Nothing Then
          symbolCode = Convert.ToInt32(r(8))
          newSymbolSize = Math.Max(GetSymbolSize(m_display, symbolCode), newSymbolSize)
        End If


        env.Union(point.Envelope)
      Next r

    ' Expand the envelope in order to include the size of the symbol
      env.Expand(newSymbolSize, newSymbolSize, False)

    'return the layer's extent in the data underlying coordinate system
      Return env
    End Function

  ''' <summary>
  ''' initialize the main table used by the layer as well as the symbols table.
    ''' The base class calls new on the table and adds a default ID field.
  ''' </summary>
    Private Sub InitializeTables()
      Dim path As String = System.IO.Path.Combine(m_dataFolder, "Weather.xml")
      'In case that there is no existing cache on the local machine, create the table.
      If (Not System.IO.File.Exists(path)) Then

        'create the table the table  in addition to the default 'ID' and 'Geometry'  
        m_table = New DataTable("RECORDS")

        m_table.Columns.Add("ID", GetType(Long)) '0
        m_table.Columns.Add("ZIPCODE", GetType(Long)) '1
        m_table.Columns.Add("CITYNAME", GetType(String)) '2
        m_table.Columns.Add("LAT", GetType(Double)) '3
        m_table.Columns.Add("LON", GetType(Double)) '4
        m_table.Columns.Add("TEMP", GetType(Integer)) '5
        m_table.Columns.Add("CONDITION", GetType(String)) '6
        m_table.Columns.Add("ICONNAME", GetType(String)) '7
        m_table.Columns.Add("ICONID", GetType(Integer)) '8
        m_table.Columns.Add("DAY", GetType(String)) '9
        m_table.Columns.Add("DATE", GetType(String)) '10
        m_table.Columns.Add("LOW", GetType(String)) '11
        m_table.Columns.Add("HIGH", GetType(String)) '12
        m_table.Columns.Add("SELECTED", GetType(Boolean)) '13
        m_table.Columns.Add("UPDATEDATE", GetType(DateTime)) '14


        'set the ID column to be auto increment
        m_table.Columns(0).AutoIncrement = True
        m_table.Columns(0).ReadOnly = True

        'the zipCode column must be the unique and nut allow null
        m_table.Columns(1).Unique = True

        ' set the ZIPCODE primary key for the table
        m_table.PrimaryKey = New DataColumn() {m_table.Columns("ZIPCODE")}

    Else 'in case that the local cache exists, simply load the tables from the cache.
        Dim ds As DataSet = New DataSet()
        ds.ReadXml(path)

        m_table = ds.Tables("RECORDS")

      If Nothing Is m_table Then
        Throw New Exception("Cannot find 'RECORDS' table")
      End If

      If 15 <> m_table.Columns.Count Then
        Throw New Exception("Table 'RECORDS' does not have all required columns")
      End If

      m_table.Columns(0).ReadOnly = True

      ' set the ZIPCODE primary key for the table
        m_table.PrimaryKey = New DataColumn() {m_table.Columns("ZIPCODE")}

        'synchronize the locations table
        For Each r As DataRow In m_table.Rows
          Try
      'in case that the locations table does not exists, create and initialize it
            If Nothing Is m_locations Then
              InitializeLocations()
            End If

      'get the zipcode for the record
            Dim zip As String = Convert.ToString(r(1))

          'make sure that there is no existing record with that zipCode already in the 
          'locations table.
          Dim rows As DataRow() = m_locations.Select("ZIPCODE = " & zip)
            If 0 = rows.Length Then
              Dim rec As DataRow = m_locations.NewRow()
              rec(1) = Convert.ToInt64(r(1)) 'zip code
              rec(2) = Convert.ToString(r(2)) 'city name

        'add the new record to the locations table
        SyncLock m_locations
                m_locations.Rows.Add(rec)
        End SyncLock
            End If
          Catch ex As Exception
            System.Diagnostics.Trace.WriteLine(ex.Message)
          End Try
        Next r

            'dispose the DS
      ds.Tables.Remove(m_table)
      ds.Dispose()
      GC.Collect()
    End If

      'initialize the symbol map table
      m_symbolTable = New DataTable("Symbology")

      'add the columns to the table
      m_symbolTable.Columns.Add("ID", GetType(Integer)) '0
      m_symbolTable.Columns.Add("ICONID", GetType(Integer)) '1
      m_symbolTable.Columns.Add("SYMBOL", GetType(ISymbol)) '2
      m_symbolTable.Columns.Add("SYMBOLWIDTH", GetType(Integer)) '3
      m_symbolTable.Columns.Add("SYMBOLHEIGHT", GetType(Integer)) '4
      m_symbolTable.Columns.Add("DYNAMICGLYPH", GetType(IDynamicGlyph)) '5
      m_symbolTable.Columns.Add("BITMAP", GetType(Bitmap)) '6

      'set the ID column to be auto increment
      m_symbolTable.Columns(0).AutoIncrement = True
      m_symbolTable.Columns(0).ReadOnly = True

      m_symbolTable.Columns(1).AllowDBNull = False
      m_symbolTable.Columns(1).Unique = True

      'set ICONID as the primary key for the table
      m_symbolTable.PrimaryKey = New DataColumn() {m_symbolTable.Columns("ICONID")}
    End Sub

  ''' <summary>
  ''' Initialize the location table. Gets the location from a featureclass
  ''' </summary>
  Private Sub InitializeLocations()
        'create a new instance of the location table
    m_locations = New DataTable()

    'add fields to the table
    m_locations.Columns.Add("ID", GetType(Integer))
    m_locations.Columns.Add("ZIPCODE", GetType(Long))
    m_locations.Columns.Add("CITYNAME", GetType(String))

    m_locations.Columns(0).AutoIncrement = True
    m_locations.Columns(0).ReadOnly = True

    'set ZIPCODE as the primary key for the table
    m_locations.PrimaryKey = New DataColumn() {m_locations.Columns("ZIPCODE")}

    'spawn a thread to populate the locations table
    Dim t As Thread = New Thread(AddressOf PopulateLocationsTableProc)
    t.Start()

    System.Threading.Thread.Sleep(1000)
  End Sub

  ''' <summary>
  ''' Load the information from the MajorCities featureclass to the locations table
  ''' </summary>
  Private Sub PopulateLocationsTableProc()
    'get the ArcGIS path from the registry
        Dim key As RegistryKey = Registry.LocalMachine.OpenSubKey("SOFTWARE\ESRI\ArcObjectsSdk10.1")
    Dim path As String = Convert.ToString(key.GetValue("InstallDir"))

        If (Not System.IO.File.Exists(System.IO.Path.Combine(path, "Samples\Data\USZipCodeData\ZipCode_Boundaries_US_Major_Cities.shp"))) Then
            MessageBox.Show("Cannot find file ZipCode_Boundaries_US_Major_Cities.shp!")
            Return
        End If

    'open the featureclass
    Dim wf As IWorkspaceFactory = New ShapefileWorkspaceFactoryClass()
        Dim ws As IWorkspace = wf.OpenFromFile(System.IO.Path.Combine(path, "Samples\Data\USZipCodeData"), 0)
    Dim fw As IFeatureWorkspace = TryCast(ws, IFeatureWorkspace)
    Dim featureClass As IFeatureClass = fw.OpenFeatureClass("ZipCode_Boundaries_US_Major_Cities")
    'map the name and zip fields
    Dim zipIndex As Integer = featureClass.FindField("ZIP")
    Dim nameIndex As Integer = featureClass.FindField("NAME")
    Dim cityName As String
    Dim zip As Long

    Try
      'iterate through the features and add the information to the table
      Dim fCursor As IFeatureCursor = Nothing
      fCursor = featureClass.Search(Nothing, True)
      Dim feature As IFeature = fCursor.NextFeature()
      Dim index As Integer = 0

      Do While Not Nothing Is feature
        Dim obj As Object = feature.Value(nameIndex)
        If obj Is Nothing Then
          Continue Do
        End If
        cityName = Convert.ToString(obj)

        obj = feature.Value(zipIndex)
        If obj Is Nothing Then
          Continue Do
        End If
        zip = Long.Parse(Convert.ToString(obj))
        If zip <= 0 Then
          Continue Do
        End If

        'add the current location to the location table
        Dim r As DataRow = m_locations.Rows.Find(zip)
        If Nothing Is r Then
          r = m_locations.NewRow()
          r(1) = zip
          r(2) = cityName
          SyncLock m_locations
            m_locations.Rows.Add(r)
          End SyncLock
        End If

        feature = fCursor.NextFeature()

        index += 1
      Loop

    'release the feature cursor
    Marshal.ReleaseComObject(fCursor)
    Catch ex As Exception
      System.Diagnostics.Trace.WriteLine(ex.Message)
    End Try
  End Sub

    ''' <summary>
    ''' Initialize the symbol that would use to highlight selected items
    ''' </summary>
  Private Sub InitializeSelectionSymbol()
    'use a character marker symbol:
    Dim chMrkSym As ICharacterMarkerSymbol
    chMrkSym = New CharacterMarkerSymbolClass()

    'Set the selection color (yellow)
    Dim color As IRgbColor
    color = New RgbColorClass()
    color.Red = 0
    color.Green = 255
    color.Blue = 255

    'set the font
    Dim aFont As stdole.IFont
    aFont = New stdole.StdFontClass()
    aFont.Name = "ESRI Default Marker"
    aFont.Size = m_symbolSize
    aFont.Bold = True

    'char #41 is just a rectangle
    chMrkSym.CharacterIndex = 41
    chMrkSym.Color = TryCast(color, IColor)
    chMrkSym.Font = TryCast(aFont, stdole.IFontDisp)
    chMrkSym.Size = m_symbolSize

    m_selectionSymbol = TryCast(chMrkSym, ISymbol)
  End Sub
  ''' <summary>
  ''' run the thread that does the update of the weather data
  ''' </summary>
  ''' <param name="sender"></param>
  ''' <param name="e"></param>
  Private Sub OnUpdateTimer(ByVal sender As Object, ByVal e As ElapsedEventArgs)
    m_timer.Interval = 2700000 '(45 minutes)
    m_updateThread = New Thread(AddressOf ThreadProc)

    'run the update thread
    m_updateThread.Start()
  End Sub

  ''' <summary>
  ''' the main update thread for the layer.
  ''' </summary>
  ''' <remarks>Since the layer gets the weather information from a web service which might
    ''' take a while to respond, it is not logical to let the application hang while waiting
    ''' for response. Therefore, running the request on a different thread frees the application to 
  ''' continue working while waiting for a response. 
  ''' Please note that in this case, synchronization of shared resources must be addressed,
  ''' otherwise you might end up getting unexpected results.</remarks>
  Private Sub ThreadProc()
    Try

      Dim lZipCode As Long
      'iterate through all the records in the main table and update it against 
      'the information from the website.
      For Each r As DataRow In m_locations.Rows
        'put the thread to sleep in order not to overwhelm yahoo web site might
        System.Threading.Thread.Sleep(200)

        'get the zip code of the record (column #1)
        lZipCode = Convert.ToInt32(r(1))

        'make the request and update the item
        AddWeatherItem(lZipCode, 0.0, 0.0)
      Next r

      'serialize the tables onto the local machine
      Dim ds As DataSet = New DataSet()
      ds.Tables.Add(m_table)
      ds.WriteXml(System.IO.Path.Combine(m_dataFolder, "Weather.xml"))
      ds.Tables.Remove(m_table)
      ds.Dispose()
      GC.Collect()

      MyBase.m_bIsCompiledDirty = True

      'fire an event to notify update of the weatheritems 
      If Not OnWeatherItemsUpdatedEvent Is Nothing Then
        RaiseEvent OnWeatherItemsUpdated(Me, New EventArgs())
      End If
    Catch ex As Exception
      System.Diagnostics.Trace.WriteLine(ex.Message)
    End Try
  End Sub

    ''' <summary>
    ''' given a bitmap url, saves it on the local machine and returns its size
    ''' </summary>
    ''' <param name="iconPath"></param>
    ''' <param name="width"></param>
    ''' <param name="height"></param>
  Private Function DownloadIcon(ByVal iconPath As String, <System.Runtime.InteropServices.Out()> ByRef width As Integer, <System.Runtime.InteropServices.Out()> ByRef height As Integer) As Bitmap
    'if the icon does not exist on the local machine, get it from RSS site
    Dim iconFileName As String = System.IO.Path.Combine(m_iconFolder, System.IO.Path.GetFileNameWithoutExtension(iconPath) & ".bmp")
    width = 0
    height = 0
    Dim bitmap As Bitmap = Nothing
    If (Not File.Exists(iconFileName)) Then
      Using webClient As System.Net.WebClient = New System.Net.WebClient()
        'open a readable stream to download the bitmap
        Using stream As System.IO.Stream = webClient.OpenRead(iconPath)
          bitmap = New Bitmap(stream, True)

          'save the image as a bitmap in the icons folder
          bitmap.Save(iconFileName, ImageFormat.Bmp)

          'get the bitmap's dimensions
          width = bitmap.Width
          height = bitmap.Height
        End Using
      End Using
    Else
      'get the bitmap's dimensions
      bitmap = New Bitmap(iconFileName)
      width = bitmap.Width
      height = bitmap.Height
    End If

    Return bitmap
  End Function

  ''' <summary>
  ''' get the specified symbol from the symbols table.
  ''' </summary>
  ''' <param name="iconCode"></param>
  ''' <param name="dbr"></param>
  ''' <returns></returns>
  Private Function GetSymbol(ByVal iconCode As Integer, ByVal dbr As DataRow) As ISymbol
    Dim symbol As ISymbol = Nothing
    Dim iconPath As String
    Dim iconWidth, iconHeight As Integer
    Dim bitmap As Bitmap = Nothing

    'search for an existing symbol in the table
    Dim r As DataRow = m_symbolTable.Rows.Find(iconCode)
    If r Is Nothing Then 'in case that the symbol does not exist in the table, create a new entry
      r = m_symbolTable.NewRow()
      r(1) = iconCode

      iconPath = Convert.ToString(dbr(7))
      'Initialize the picture marker symbol
      symbol = InitializeSymbol(iconPath, iconWidth, iconHeight, bitmap)
      If Nothing Is symbol Then
        Return Nothing
      End If

      'update the symbol table
      SyncLock m_symbolTable
        r(2) = symbol
        r(3) = iconWidth
        r(4) = iconHeight
        r(6) = bitmap
        m_symbolTable.Rows.Add(r)
      End SyncLock
    Else
      If TypeOf r(2) Is DBNull Then  'in case that the record exists but the symbol hasn't been initialized
        iconPath = Convert.ToString(dbr(7))
        'Initialize the picture marker symbol
        symbol = InitializeSymbol(iconPath, iconWidth, iconHeight, bitmap)
        If Nothing Is symbol Then
          Return Nothing
        End If

        'update the symbol table
        SyncLock m_symbolTable
          r(2) = symbol
          r(6) = bitmap
          r.AcceptChanges()
        End SyncLock
      Else 'the record exists in the table and the symbol has been initialized
        'get the symbol
        symbol = TryCast(r(2), ISymbol)
      End If
    End If

    'return the requested symbol
    Return symbol
  End Function

  Private Function GetDynamicGlyph(ByVal dynamicGlyphFactory As IDynamicGlyphFactory2, ByVal iconCode As Integer, ByVal dbr As DataRow, <System.Runtime.InteropServices.Out()> ByRef originalIconSize As Integer) As IDynamicGlyph
    originalIconSize = 0

    If dynamicGlyphFactory Is Nothing Then
      Return Nothing
    End If

    Dim iconPath As String
    Dim iconWidth, iconHeight As Integer
    Dim bitmap As Bitmap = Nothing
    Dim dynamicGlyph As IDynamicGlyph = Nothing

    'search for an existing symbol in the table
    Dim r As DataRow = m_symbolTable.Rows.Find(iconCode)
    If r Is Nothing Then
      iconPath = Convert.ToString(dbr(7))
      bitmap = DownloadIcon(iconPath, iconWidth, iconHeight)
      If Not bitmap Is Nothing Then
        originalIconSize = iconWidth

                dynamicGlyph = dynamicGlyphFactory.CreateDynamicGlyphFromBitmap(esriDynamicGlyphType.esriDGlyphMarker, bitmap.GetHbitmap().ToInt32(), False, CType(ESRI.ArcGIS.ADF.Connection.Local.Converter.ToRGBColor(Color.FromArgb(255, 255, 255)), IColor))


        'update the symbol table
        r = m_symbolTable.NewRow()
        SyncLock m_symbolTable
          r(1) = iconCode
          r(3) = iconWidth
          r(4) = iconHeight
          r(5) = dynamicGlyph
          r(6) = bitmap
          m_symbolTable.Rows.Add(r)
        End SyncLock
      End If
    Else
      If TypeOf r(5) Is DBNull Then
        If TypeOf r(6) Is DBNull Then
          iconPath = Convert.ToString(dbr(7))
          bitmap = DownloadIcon(iconPath, iconWidth, iconHeight)
          If bitmap Is Nothing Then
            Return Nothing
          End If

          originalIconSize = iconWidth

          SyncLock m_symbolTable
            r(3) = iconWidth
            r(4) = iconHeight
            r(6) = bitmap
          End SyncLock
        Else
          originalIconSize = Convert.ToInt32(r(3))
          bitmap = CType(r(6), Bitmap)
        End If
                dynamicGlyph = dynamicGlyphFactory.CreateDynamicGlyphFromBitmap(esriDynamicGlyphType.esriDGlyphMarker, bitmap.GetHbitmap().ToInt32(), False, CType(ESRI.ArcGIS.ADF.Connection.Local.Converter.ToRGBColor(Color.FromArgb(255, 255, 255)), IColor))

        SyncLock m_symbolTable
          r(5) = dynamicGlyph
        End SyncLock
      Else
        originalIconSize = Convert.ToInt32(r(3))
        dynamicGlyph = CType(r(5), IDynamicGlyph)
      End If
    End If

    Return dynamicGlyph
  End Function


    ''' <summary>
  ''' Initialize a character marker symbol for a given bitmap path
    ''' </summary>
    ''' <param name="iconPath"></param>
    ''' <param name="iconWidth"></param>
    ''' <param name="iconHeight"></param>
    ''' <returns></returns>
  Private Function InitializeSymbol(ByVal iconPath As String, <System.Runtime.InteropServices.Out()> ByRef iconWidth As Integer, <System.Runtime.InteropServices.Out()> ByRef iconHeight As Integer, <System.Runtime.InteropServices.Out()> ByRef bitmap As Bitmap) As ISymbol
    iconWidth = 0
    iconHeight = 0
    bitmap = Nothing
    Try
      'make sure that the icon exit on dist or else download it
      bitmap = DownloadIcon(iconPath, iconWidth, iconHeight)
      Dim iconFileName As String = System.IO.Path.Combine(m_iconFolder, System.IO.Path.GetFileNameWithoutExtension(iconPath) & ".bmp")
      If (Not System.IO.File.Exists(iconFileName)) Then
        Return Nothing
      End If

      'initialize the transparent color
      Dim rgbColor As IRgbColor = New RgbColorClass()
      rgbColor.Red = 255
      rgbColor.Blue = 255
      rgbColor.Green = 255

      'instantiate the marker symbol and set its properties
      Dim pictureMarkerSymbol As IPictureMarkerSymbol = New PictureMarkerSymbolClass()
      pictureMarkerSymbol.CreateMarkerSymbolFromFile(ESRI.ArcGIS.Display.esriIPictureType.esriIPictureBitmap, iconFileName)
      pictureMarkerSymbol.Angle = 0
      pictureMarkerSymbol.Size = m_symbolSize
      pictureMarkerSymbol.XOffset = 0
      pictureMarkerSymbol.YOffset = 0
      pictureMarkerSymbol.BitmapTransparencyColor = TryCast(rgbColor, IColor)

      'return the symbol
      Return CType(pictureMarkerSymbol, ISymbol)
    Catch
      Return Nothing
    End Try
  End Function

  ''' <summary>
  ''' Makes a request against RSS Weather service and add update the layer's table
  ''' </summary>
  ''' <param name="zipCode"></param>
  ''' <param name="Lat"></param>
  ''' <param name="Lon"></param>
    Private Sub AddWeatherItem(ByVal zipCode As Long, ByVal Lat As Double, ByVal Lon As Double)
      Try
        Dim cityName As String
        Dim newLat, newLon As Double
        Dim temp As Integer
        Dim condition As String
        Dim desc As String
        Dim iconPath As String
        Dim day As String
        Dim [date] As String
        Dim low As Integer
        Dim high As Integer
        Dim iconCode As Integer
        Dim iconWidth As Integer = 52 'default values
        Dim iconHeight As Integer = 52
        Dim bitmap As Bitmap = Nothing

        Dim dbr As DataRow = m_table.Rows.Find(zipCode)
        If Not dbr Is Nothing Then
          ' get the date 
          Dim updateDate As DateTime = Convert.ToDateTime(dbr(14))
          Dim ts As TimeSpan = DateTime.Now.Subtract(updateDate)

          ' if the item had been updated in the past 15 minutes, simply bail out.
          If ts.TotalMinutes < 15 Then
            Return
          End If
        End If

      'the base URL for the service
        Dim url As String = "http://xml.weather.yahoo.com/forecastrss?p="
      'the RegEx used to extract the icon path from the HTML tag
        Dim regxQry As String = "(http://(\"")?(.*?\.gif))"
        Dim reader As XmlTextReader = Nothing
        Dim doc As XmlDocument
        Dim node As XmlNode

        Try  
        'make the request and get the result back into XmlReader
          reader = New XmlTextReader(url & zipCode.ToString())
        Catch ex As Exception
          System.Diagnostics.Trace.WriteLine(ex.Message)
          Return
        End Try

      'load the XmlReader to an xml doc
        doc = New XmlDocument()
        doc.Load(reader)

      'set an XmlNamespaceManager since we have to make explicit namespace searches
      Dim xmlnsManager As XmlNamespaceManager = New System.Xml.XmlNamespaceManager(doc.NameTable)
      'Add the namespaces used in the xml doc to the XmlNamespaceManager.
      xmlnsManager.AddNamespace("yweather", "http://xml.weather.yahoo.com/ns/rss/1.0")
      xmlnsManager.AddNamespace("geo", "http://www.w3.org/2003/01/geo/wgs84_pos#")

      'make sure that the node exists
      node = doc.DocumentElement.SelectSingleNode("/rss/channel/yweather:location/@city", xmlnsManager)
      If Nothing Is node Then
        Return
      End If

      'get the cityname
      cityName = doc.DocumentElement.SelectSingleNode("/rss/channel/yweather:location/@city", xmlnsManager).InnerXml
      If Lat = 0.0 AndAlso Lon = 0.0 Then
                'in case that the caller did not specify a coordinate, get the default coordinate from the service
        newLat = Convert.ToDouble(doc.DocumentElement.SelectSingleNode("/rss/channel/item/geo:lat", xmlnsManager).InnerXml)
        newLon = Convert.ToDouble(doc.DocumentElement.SelectSingleNode("/rss/channel/item/geo:long", xmlnsManager).InnerXml)
      Else
        newLat = Lat
        newLon = Lon
      End If

      'extract the rest of the information from the RSS response
        condition = doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:condition/@text", xmlnsManager).InnerXml
        iconCode = Convert.ToInt32(doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:condition/@code", xmlnsManager).InnerXml)
        temp = Convert.ToInt32(doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:condition/@temp", xmlnsManager).InnerXml)
        desc = doc.DocumentElement.SelectSingleNode("/rss/channel/item/description").InnerXml
        day = doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:forecast/@day", xmlnsManager).InnerXml
        [date] = doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:forecast/@date", xmlnsManager).InnerXml
        low = Convert.ToInt32(doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:forecast/@low", xmlnsManager).InnerXml)
        high = Convert.ToInt32(doc.DocumentElement.SelectSingleNode("/rss/channel/item/yweather:forecast/@high", xmlnsManager).InnerXml)


        'use regex in order to extract the icon name from the html script
        Dim m As Match = Regex.Match(desc,regxQry)
        If m.Success Then
          iconPath = m.Value

          'add the icon ID to the symbology table
          Dim tr As DataRow = m_symbolTable.Rows.Find(iconCode)
          If Nothing Is tr Then
            'get the icon from the website
            bitmap = DownloadIcon(iconPath, iconWidth, iconHeight)

                    'create a new record
            tr = m_symbolTable.NewRow()
            tr(1) = iconCode
            tr(3) = iconWidth
            tr(4) = iconHeight
            tr(6) = bitmap

        'update the symbol table. The initialization of the symbol cannot take place in here, since
                    'this code gets executed on a background thread.
            SyncLock m_symbolTable
              m_symbolTable.Rows.Add(tr)
            End SyncLock
          Else 'get the icon's dimensions from the table
                    'get the icon's dimensions from the table
            iconWidth = Convert.ToInt32(tr(3))
            iconHeight = Convert.ToInt32(tr(4))
          End If
        Else
          iconPath = ""
        End If

      'test whether the record already exists in the layer's table.
            If Nothing Is dbr Then 'in case that the record does not exist
                'create a new record
                dbr = m_table.NewRow()

                If (Not m_table.Columns(0).AutoIncrement) Then
                    dbr(0) = Convert.ToInt32(DateTime.Now.Millisecond)
                End If

                'add the item to the table
                SyncLock m_table
                    dbr(1) = zipCode
                    dbr(2) = cityName
                    dbr(3) = newLat
                    dbr(4) = newLon
                    dbr(5) = temp
                    dbr(6) = condition
                    dbr(7) = iconPath
                    dbr(8) = iconCode
                    dbr(9) = day
                    dbr(10) = [date]
                    dbr(11) = low
                    dbr(12) = high
                    dbr(13) = False
                    dbr(14) = DateTime.Now

                    m_table.Rows.Add(dbr)
                End SyncLock
            Else 'in case that the record exists, just update it
                'update the record
                SyncLock m_table
                    dbr(5) = temp
                    dbr(6) = condition
                    dbr(7) = iconPath
                    dbr(8) = iconCode
                    dbr(9) = day
                    dbr(10) = [date]
                    dbr(11) = low
                    dbr(12) = high
                    dbr(14) = DateTime.Now

                    dbr.AcceptChanges()
                End SyncLock
            End If

        MyBase.m_bIsCompiledDirty = True

        'fire an event to notify the user that the item has been updated
    If Not OnWeatherItemAddedEvent Is Nothing Then
      Dim weatherItemEventArgs As WeatherItemEventArgs = New WeatherItemEventArgs(Convert.ToInt32(dbr(0)), zipCode, newLon, newLat, iconWidth, iconHeight)
      RaiseEvent OnWeatherItemAdded(Me, weatherItemEventArgs)
    End If

    Catch ex As Exception
      System.Diagnostics.Trace.WriteLine("AddWeatherItem: " & ex.Message)
    End Try
  End Sub
  #End Region

  #Region "IIdentify Members"

  ''' <summary>
  ''' Identifying all the weather items falling within the given envelope
  ''' </summary>
  ''' <param name="pGeom"></param>
  ''' <returns></returns>
  Public Function Identify(ByVal pGeom As IGeometry) As IArray Implements IIdentify.Identify
    Dim intersectEnv As IEnvelope = New EnvelopeClass()
    Dim inEnv As IEnvelope
    Dim array As IArray = New ArrayClass()

        'get the envelope from the geometry 
    If pGeom.GeometryType = esriGeometryType.esriGeometryEnvelope Then
      inEnv = pGeom.Envelope
    Else
      inEnv = TryCast(pGeom, IEnvelope)
    End If

    'reproject the envelope to the source coordsys
    'this would allow to search directly on the Lat/Lon columns
      If Not Nothing Is m_spatialRef AndAlso m_mapSpatialRef.FactoryCode <> m_layerSRFactoryCode AndAlso Not Nothing Is inEnv.SpatialReference Then
        inEnv.Project(MyBase.m_spatialRef)
      End If

    'expand the envelope so that it'll cover the symbol
    inEnv.Expand(4,4,True)

    Dim xmin, ymin, xmax, ymax As Double
    inEnv.QueryCoords(xmin, ymin, xmax, ymax)

    'select all the records within the given extent
    Dim qry As String = "LON >= " & xmin.ToString() & " AND LON <= " & xmax.ToString() & " AND Lat >= " & ymin.ToString() & " AND LAT <= " & ymax.ToString()
    Dim rows As DataRow() = m_table.Select(qry)
    If 0 = rows.Length Then
      Return array
    End If

    Dim zipCode As Long
    Dim propSet As IPropertySet = Nothing
    Dim idObj As IIdentifyObj = Nothing
    Dim idObject As IIdentifyObject = Nothing
    Dim bIdentify As Boolean = False

    For Each r As DataRow In rows
    'get the zipCode
    zipCode = Convert.ToInt64(r("ZIPCODE"))

    'get the properties of the given item in order to pass it to the identify object
    propSet = Me.GetWeatherItem(zipCode)
    If Not Nothing Is propSet Then
      'instantiate the identify object and add it to the array
      idObj = New RSSWeatherIdentifyObject()
      'test whether the layer can be identified
      bIdentify = idObj.CanIdentify(CType(Me, ILayer))
      If bIdentify Then
        idObject = TryCast(idObj, IIdentifyObject)
        idObject.PropertySet = propSet
        array.Add(idObj)
      End If
    End If
    Next r

    'return the array with the identify objects
    Return array
  End Function

    Private Function GetSymbolSize(ByVal display As IDisplay, ByVal symbolCode As Integer) As Double
      If display Is Nothing Then
        Return 0
      End If

      Dim newSymbolSize As Double = 0
      Dim symbolSizePixels As Double = 0
      Dim r As DataRow = m_symbolTable.Rows.Find(symbolCode)
      If Not r Is Nothing Then
        symbolSizePixels = Convert.ToDouble(m_symbolSize)

            ' convert the symbol size from pixels to map units
        Dim transform As ITransformation = TryCast(display.DisplayTransformation, ITransformation)
        If transform Is Nothing Then
          Return 0
        End If

        Dim symbolDimensions As Double() = New Double(1){}
        symbolDimensions(0) = CDbl(symbolSizePixels)
        symbolDimensions(1) = CDbl(symbolSizePixels)

        Dim symbolDimensionsMap As Double() = New Double(1){}

        transform.TransformMeasuresFF(esriTransformDirection.esriTransformReverse, 1, symbolDimensionsMap(0), symbolDimensions(0))
        newSymbolSize = symbolDimensionsMap(0)
      End If

      Return newSymbolSize
    End Function

  #End Region
  End Class