WPF Multi-Threading and rotating image - wpf

Question

This one has driven me nuts for long enough.
Start a background thread to download data from a webservice on a new thread then show an image on the status bar and change the text.
I have tried with Dispatcher (with each priority) but nothing happens until the threaded sub completes. The closest I can get is implementing the equivalent of DoEvents that at least loads the image and the text, but then the image stops spinning until the thread completes.
Any ideas?
Public Sub Return_DT(ByVal TableName As String)
CurrentDT = TableName
If DownloadingDS Is Nothing Then
DownloadingDS = New Dictionary(Of String, String)
End If
If DownloadingDS.ContainsKey(TableName) = False Then
DownloadingDS.Add(TableName, "Loading")
Else
Exit Sub
End If
Select Case TableName
Case "A_Documents"
strSQL = "SELECT Document_ID, Account_Type, Account_No, Document_Description, Accounts_Only, Open_Editing, Editing_Name, Updated_Name, Updated FROM A_Documents"
Case Else
strSQL = "SELECT * FROM " & TableName
End Select
' Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, CType(Sub() LoadMetroImage(), SendOrPostCallback), Nothing)
'Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, CType(Sub() ChangeLeftStatusText("Downloading " & CurrentDT & " data..."), SendOrPostCallback), Nothing)
LoadMetroImage()
ChangeLeftStatusText("Downloading " & CurrentDT & " data...")
Application.Current.MainWindow.FindName("MainMetroStatusBar")
Dim vWorker As New BackgroundWorker
AddHandler vWorker.DoWork, AddressOf BackgroundDownload
AddHandler vWorker.RunWorkerCompleted, AddressOf DownloadCompleted
vWorker.RunWorkerAsync()
DoEvents()
End Sub
This is the closest I can get
Public Sub DoEvents()
Dim frame As New DispatcherFrame()
Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, New DispatcherOperationCallback(AddressOf ExitFrame), frame)
Dispatcher.PushFrame(frame)
End Sub
Public Function ExitFrame(ByVal f As Object) As Object
CType(f, DispatcherFrame).Continue = False
Return Nothing
End Function
=== EDIT === How Return_DT is called
Public Function DT_Return(ByVal DT As DataTable, ByVal TableName As String) As DataTable
Try
If Not DT Is Nothing Then
If DT_CheckUpdated(TableName) = True Then
Return DT
Else
Return_DT(TableName)
vService = New Service1Client
Dim DS As DataSet = vService.ReturnDataSet("SELECT * FROM " & TableName, Current_HOA_ID)
Dim vDT As DataTable = DS.Tables(0).Copy
DS.Dispose()
Return vDT
End If
Else
Return_DT(TableName)
vService = New Service1Client
Dim DS As DataSet = vService.ReturnDataSet("SELECT * FROM " & TableName, Current_HOA_ID)
Dim vDT As DataTable = DS.Tables(0).Copy
DS.Dispose()
Return vDT
End If
Catch ex As Exception
EmailError(ex)
Return Nothing
End Try
End Function

Answer 1

I found the solution was to use Dispatcher.Timer in the UI thread to check every second to see if the DT had been downloaded..
Public Function DT_Return(ByVal DT As DataTable, ByVal TableName As String) As DataTable
Try
If Not DT Is Nothing Then
If DT_CheckUpdated(TableName) = True Then
Return DT
Else
CurrentlyDownloading = True
Return_DT(TableName)
Dim vTimer As New DispatcherTimer
vTimer.Interval = TimeSpan.FromMilliseconds(1000)
AddHandler vTimer.Tick, Sub(sender As Object, e As EventArgs)
Do While CurrentlyDownloading = True
Loop
vTimer.Stop()
End Sub
vTimer.Start()
Return DT
End If
Else
CurrentlyDownloading = True
Return_DT(TableName)
Dim vTimer As New DispatcherTimer
vTimer.Interval = TimeSpan.FromMilliseconds(1000)
AddHandler vTimer.Tick, Sub(sender As Object, e As EventArgs)
Do While CurrentlyDownloading = True
Loop
vTimer.Stop()
End Sub
vTimer.Start()
Return DT
End If
Catch ex As Exception
EmailError(ex)
Return Nothing
End Try
End Function