Question

I am trying to create a dialog box that shows the process of loading certain bill data to Word from a WPF VB.NET app. The problem is that the WPF UI is not updating to show the change.

WPF Code is:

    <StackPanel Grid.Row="1" HorizontalAlignment="Center" VerticalAlignment="Center" >
        <TextBlock Name="StatusDisplayTextBlock" Text="Printing 30 of 40 to document......" FontSize="20"/>
        <ProgressBar Name="PrintProgressBar1" Height="30" Width="400" Margin="0,10,0,0"/>
    </StackPanel>

VB.NET Code:

Imports Microsoft.Office.Interop

Public Class PrintingToDocx
    Dim IsWorkDone As Boolean = False
    Public Enum BillPrintMode
        InOne = 0
        Seperate = 1
    End Enum

    Private BrowserBills As New List(Of Classes.BillsNS.BilBrowserClass)
    Private Bills As New List(Of Classes.BillsNS.BillClass)
    Private PrintMode As BillPrintMode

    Private Sub PrintingToDocx_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles Me.Closing
        If IsWorkDone = False Then
            e.Cancel = True
        End If
    End Sub

    Public Sub New(ByVal BrowserBills As List(Of Classes.BillsNS.BilBrowserClass), ByVal Mode As BillPrintMode)
        InitializeComponent()
        Me.BrowserBills = BrowserBills
        PrintMode = Mode
    End Sub

    Private Sub Window_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
        GetBills()
        If PrintMode = BillPrintMode.InOne Then
            PrintInOne()
            ' IsWorkDone = True
        Else
            Dim count As Integer = 0
            For Each k In Bills
                count = count + 1
                StatusDisplayTextBlock.Text = "Writing Bill " & count & " of " & Bills.Count & " to WORD....."
                DataAccessModuleNS.Reports.PrintaBill(k)
            Next
            IsWorkDone = True
        End If
        Me.Close()
    End Sub

    Private Sub GetBills()
        Me.Focus()
        StatusDisplayTextBlock.Text = "Reading Bills Data...."
        Dim count As Integer = 1
        For Each k In BrowserBills
            Bills.Add(DataAccessModuleNS.Bills.GetBill(k.ID.ToString))
            StatusDisplayTextBlock.Text = "Reading Bill " & count & " of " & BrowserBills.Count & "...."
            'count = count + 1
            count += 1
        Next
    End Sub

    Private Sub PrintInOne()
        Try
            StatusDisplayTextBlock.Text = "Writing Bill " & "0" & " of " & Bills.Count & " to WORD....."

            Dim oWord As Word.Application
            Dim oDoc As Word.Document
            Dim oTable As Word.Table

            Me.Focus()
            'Start Word and open the document template.
            oWord = CreateObject("Word.Application")
            oWord.Visible = False
            oDoc = oWord.Documents.Add
            Dim countBills As Integer = 0
            For Each Bill In Bills
                'To Addressing Fields
                countBills = countBills + 1
                StatusDisplayTextBlock.Text = "Writing Bill " & countBills & " of " & Bills.Count & " to WORD....."

    End Sub
End Class

The problem is like this:
The functionality if working fine, but the UI is not displaying until all the processing is complete. Following is the sample image of taskbar at time of processing to word:

when work is done it is working fine like this:

Following is the Report

EDIT: I now used the background worker, but now the issue is that when the progress changed and I try to update the TextBlock on UI thread I get the error that the action on a different thread cannot be done. Following is the code I used in ProgressChanged event.

Private Sub BackgroundWorker_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs)
    'Throw New NotImplementedException
    StatusDisplayTextBlock.Text = e.UserState
End Sub

Could you please help me in figuring out how to update the UI thread.

Answer 1

You need to move the logic operation from UI thread…

Best solution would be to use Backgroundworker class to separate all operations from the UI.
Good tutorial on that can be found here [link]

If by change you can use .NET 4.5, you can simlpy use Async-Await pattern [Async in VB]