multithreading a function

Imports System.Threading.Tasks
Class MainWindow
    Sub test0()
        'simulating some process
        System.Threading.Thread.Sleep(1000)
    End Sub
    Sub test1()
        'simulating some process
        System.Threading.Thread.Sleep(1000)
    End Sub
    Private Sub Button1_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles Button1.Click
        'you can even try duplicating the same function
        Dim taskA = New Task(Sub() test0(), Sub() test1())
        ' Start the task
        taskA.Start()
        'waiting for the task to complete, if you checked the status in less than 1000 it will be running still
        'but if you checked the status alittle more than 1000 say 1010 it will be completed (for the two functions)
        System.Threading.Thread.Sleep(1010)
        TextBox1.Text += taskA.Status.ToString
    End Sub

End Class

System.InvalidOperationException was unhandled by user code<br />
  Message=The calling thread must be STA, because many UI components require this.<br />
  Source=PresentationCore<br />
  StackTrace:<br />
       at System.Windows.Input.InputManager..ctor()<br />
       at System.Windows.Input.InputManager.GetCurrentInputManagerImpl()<br />
       at System.Windows.Input.KeyboardNavigation..ctor()<br />
       at System.Windows.FrameworkElement.FrameworkServices..ctor()<br />
       at System.Windows.FrameworkElement.EnsureFrameworkServices()<br />
       at System.Windows.FrameworkElement..ctor()<br />
       at System.Windows.Controls.Viewport3D..ctor()<br />
       at WpfApplication1.MainWindow.TextOverImg(ImageSource imagePlate, String imgSave, Double trans, FormattedText fText, FormattedText sText, String[] imgCoords, Int32 Lines) in C:\Users\CRAX\Documents\Visual Studio 2010\Projects\task test\MainWindow.xaml.vb:line 59<br />
       at WpfApplication1.MainWindow._Closure$__1._Lambda$__1() in C:\Users\CRAX\Documents\Visual Studio 2010\Projects\task test\MainWindow.xaml.vb:line 313<br />
       at System.Threading.Tasks.Task.InnerInvoke()<br />
       at System.Threading.Tasks.Task.Execute()<br />
  InnerException: 

Public Function TextOverImg(imagePlate As ImageSource, ByVal imgSave As String,
           ByVal trans As Double, ByVal fText As FormattedText, ByVal sText As FormattedText,
	     ByVal imgCoords() As String, ByVal Lines As Integer)
 
    'whole drawing area
    Dim rec As Rect = New Rect(0, 0, 720, 576)
 
    'text drawing size
    Dim txtRec As Rect = New Rect(0, 0, 1000, 1000)
 
    Dim dvText As New DrawingVisual()
    Dim dcText As DrawingContext = dvText.RenderOpen()

    'scale bitmap for better antialiasing
    Dim sc As Integer = 300 / 96
 
      'changing texture width to single lines width
      txtRec = New Rect(0, 0, fText.MaxTextWidth, fText.Height)
 
      fText.TextAlignment = TextAlignment.Center
      sText.TextAlignment = TextAlignment.Center
 
      'reading text transperancy
      Dim trns As String = 100
 
      dcText.DrawRectangle(Brushes.WhiteSmoke, New Pen(Brushes.Black, 10.0), txtRec)
      dcText.DrawText(sText, New Point(txtRec.X + 3, txtRec.Y + 3))
      dcText.DrawText(fText, New Point(txtRec.X, txtRec.Y))
    dcText.Close()
 
    'bitmap from text
    Dim textPlate As New RenderTargetBitmap(720, 576, 96, 96, PixelFormats.Pbgra32)
    textPlate.Render(dvText)
 
      'loading coords and transforming textplate accordingly 
      If Not (trans = 0) Then
 
        'definning the viewport
        Dim viewport3d As New Viewport3D
        viewport3d.Width = rec.Width
        viewport3d.Height = rec.Height
        viewport3d.Measure(New Size(rec.Width, rec.Height))
        viewport3d.Arrange(rec)
 
        'define camera
        Dim cam As New OrthographicCamera
        cam.Position = New Point3D(0.5, 0.5, 1)
        viewport3d.Camera = cam
 
        Dim mv3d As New ModelVisual3D
        Dim mgrp3d As New Model3DGroup
        Dim gm3d As New GeometryModel3D
 
        'define light
        Dim light As New AmbientLight
        light.Color = Colors.White
        mgrp3d.Children.Add(light)
 
        'define mesh object
        Dim mesh3d As New MeshGeometry3D()
        Dim meshpoints As New Point3DCollection
        mesh3d.Positions.Add(New Point3D(0, 0, 0))
        mesh3d.Positions.Add(New Point3D(0, 1, 0))
        mesh3d.Positions.Add(New Point3D(1, 0, 0))
        mesh3d.Positions.Add(New Point3D(1, 1, 0))
 
        mesh3d.TextureCoordinates.Add(New Point(0, 1))
        mesh3d.TextureCoordinates.Add(New Point(0, 0))
        mesh3d.TextureCoordinates.Add(New Point(1, 1))
        mesh3d.TextureCoordinates.Add(New Point(1, 0))
 
        mesh3d.TriangleIndices.Add(0)
        mesh3d.TriangleIndices.Add(2)
        mesh3d.TriangleIndices.Add(1)
        mesh3d.TriangleIndices.Add(2)
        mesh3d.TriangleIndices.Add(3)
        mesh3d.TriangleIndices.Add(1)
 
        ' Apply the mesh to the geometry model.
        gm3d.Geometry = mesh3d
 
        ' Define material and apply to the mesh geometries.
        Dim mat As New DiffuseMaterial
        mat.Brush = New ImageBrush(textPlate)
        gm3d.Material = mat
 
        'new context for merging image under transformed text
        Dim dvMerge As New DrawingVisual()
        Dim dcMerge As DrawingContext = dvMerge.RenderOpen()
 
        'adding imgPlate 1st
        dcMerge.DrawImage(imagePlate, rec)
 
        Dim imgC() As String = imgCoords(0).Split("&")
        Dim imgCoordsln() As String = imgC(2).Split(Environment.NewLine)
 
        Dim pointsTransformed As Point3D() = New Point3D(3) {}
        'setting the points to array
        For i = 1 To 4 Step 1
          Dim points() As String
          points = imgCoordsln(i).Split(",")
          pointsTransformed(i - 1) = New Point3D(Val(points(0)), Val(points(1)), Val(points(2)))
        Next
        Dim xfrm As New MatrixTransform3D
 
        'transforming the geometry
        xfrm.Matrix = CalculateNonAffineTransform(pointsTransformed)
        gm3d.Transform = xfrm
        mgrp3d.Children.Add(gm3d)
        mv3d.Content = mgrp3d
        viewport3d.Children.Add(mv3d)
        
	dcMerge.Close()
 
        'rendering viewport3D to image
        Dim Mergedbmp As New RenderTargetBitmap(720 * sc, 576 * sc, 96 * sc, 96 * sc, PixelFormats.Pbgra32)
        Mergedbmp.Render(dvMerge)
        Mergedbmp.Render(viewport3d)
 
        'resizing to custom size
        Dim imgResize As New TransformedBitmap()
        imgResize.BeginInit()
        imgResize.Source = Mergedbmp
        imgResize.Transform = New ScaleTransform(0.3335, 0.3335)
        imgResize.EndInit()
 
        'path to save
        Dim path As String = imgSave
        Dim fs As FileStream = New FileStream(path, FileMode.Create)
 
        'encoding to PNG and saving
        Dim encoder As BitmapEncoder = New PngBitmapEncoder()
        encoder.Frames.Add(BitmapFrame.Create(imgResize))
        encoder.Save(fs)
 
        'preview exported image
        Return Mergedbmp
    End If
    Return imagePlate
  End Function