The attached project is a WPF application written in C# and XAML. It uses OpenFileDialog to browse text files and once text file is selected, it is loaded in a FlowDocumentReader that allows you to view, paging, and find options.

First, let's create a UI with a TextBox, a Button, and a FlowDocumentViewer control.

The UI looks like Figure 1.

fdrImg1.jpg
Figure 1

The XAML code for the UI looks like this. 

<Window x:Class="LoadTextFileInFlowDocumentViewerSample.Window1" 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        Title="Window1" Height="290" Width="600"> 
    <Canvas> 
        <TextBox Height="32" HorizontalAlignment="Left" Margin="6,10,0,0" Name="FileNameTextBox" 
                 VerticalAlignment="Top" Width="393" /> 
        <Button Content="Browse" Height="32" HorizontalAlignment="Left" Margin="405,10,0,0" 
                Name="button1" VerticalAlignment="Top" Width="88" Click="button1_Click" /> 
      
            <FlowDocumentReader Name="FlowDocReader" Background="LightBlue" 
                                Canvas.Top="50" Canvas.Left="5" Width="560" 
                                Height="210"> 
        </FlowDocumentReader> 
    </Canvas> 
</Window>


On Button control, we will browse a text file and set TextBox.Text property to the selected file. As you can see from code below, we create a Paragraph and add the selected text file using Paragraph.Inlines.Add method. After that, we create a FlowDocument by passing this Paragraph and in the end; we set FlowDocumentReader.Document property to the FlowDocument.

Code sample in C#: 

private void button1_Click(object sender, RoutedEventArgs e) 
{ 
    // Create OpenFileDialog 
    Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();           
   
    // Set filter for file extension and default file extension 
    dlg.DefaultExt = ".txt"; 
    dlg.Filter = "Text documents (.txt)|*.txt"; 
  
    // Display OpenFileDialog by calling ShowDialog method 
    Nullable<bool> result = dlg.ShowDialog(); 
  
    // Get the selected file name and display in a TextBox 
    if (result == true) 
    { 
        // Open document 
        string filename = dlg.FileName; 
        FileNameTextBox.Text = filename; 
  
        Paragraph paragraph = new Paragraph(); 
        paragraph.Inlines.Add(System.IO.File.ReadAllText(filename)); 
        FlowDocument document = new FlowDocument(paragraph); 
        FlowDocReader.Document = document; 
    } 
}

Code sample in VB.NET: 

Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) 
        'Create OpenFileDialog 
        Dim dlg As Microsoft.Win32.OpenFileDialog = New Microsoft.Win32.OpenFileDialog() 
  
        ' Set filter for file extension and default file extension 
        dlg.DefaultExt = ".txt" 
        dlg.Filter = "Text documents (.txt)|*.txt" 
  
        ' Display OpenFileDialog by calling ShowDialog method 
        If (dlg.ShowDialog() = True) Then 
  
            '; Open document 
            Dim filename As String = dlg.FileName 
            FileNameTextBox.Text = filename 
  
            Dim paragraph As Paragraph = New Paragraph() 
            paragraph.Inlines.Add(System.IO.File.ReadAllText(filename)) 
            Dim document As FlowDocument = New FlowDocument(paragraph) 
            FlowDocReader.Document = document 
        End If 
  
    End Sub

Now if you run the application and browse a text file, the output looks like Figure 2.

fdrImg2.jpg
Figure 2