<Window x:Class="MainWin"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWin" Height="371" Width="595" Loaded="Window_Loaded">
 
    <Window.CommandBindings>
        <CommandBinding Command="ApplicationCommands.Open" _
          Executed="Open_Executed" />
        <CommandBinding Command="ApplicationCommands.Save" _
        Executed="Save_Executed" />
    </Window.CommandBindings>
 
    <Grid>
        <ToolBar Margin="0,0,126,305">
            <Button Command="ApplicationCommands.Open" Content="Open" />
            <Button Command="ApplicationCommands.Save" Content="Save"/>
            <Separator />
            <ToggleButton Command="EditingCommands.ToggleBold" x:Name="btnBold" _
              Content="Fett"  /> 
            <ToggleButton Command="EditingCommands.ToggleItalic" _
            x:Name="btnItalic" Content="kursiv" />
            <ToggleButton Command="EditingCommands.ToggleUnderline" _
            x:Name="btnUnderline" Content="unterstrichen" FontFamily="Arial"  />
            <Separator />
            <ComboBox x:Name="cmbFontFamily" Width="150" _
              SelectionChanged="cmbFontFamily_SelectionChanged" />
            <ComboBox x:Name="cmbFontSize" Width="50" IsEditable="True" _
            TextBoxBase.TextChanged="cmbFontSize_TextChanged" />
        </ToolBar>
 
        <RichTextBox x:Name="rtbEditor" _
          SelectionChanged="rtbEditor_SelectionChanged" Margin="45,117,240,71" />
 
    </Grid>
</Window>

Imports System.IO
Imports Microsoft.Win32
 
Public Class MainWin
 
    Private Sub Window_Loaded(sender As Object, e As RoutedEventArgs)
 
        cmbFontFamily.ItemsSource = Fonts.SystemFontFamilies.OrderBy(Function( _
          f) f.Source)
        cmbFontSize.ItemsSource = New List(Of Double)() From {8, 9, 10, 11, 12, _
        14, 16, 18, 20, 22, 24, 26, 28, 36, 48, 72}
 
 
    End Sub
 
    Private Sub rtbEditor_SelectionChanged(sender As Object, e As _
      RoutedEventArgs)
 
        Dim temp As Object = rtbEditor.Selection.GetPropertyValue( _
          Inline.FontWeightProperty)
        btnBold.IsChecked = (temp IsNot DependencyProperty.UnsetValue) AndAlso ( _
        temp.Equals(FontWeights.Bold))
        temp = rtbEditor.Selection.GetPropertyValue(Inline.FontStyleProperty)
        btnItalic.IsChecked = (temp IsNot DependencyProperty.UnsetValue) _
          AndAlso (temp.Equals(FontStyles.Italic))
        temp = rtbEditor.Selection.GetPropertyValue( _
        Inline.TextDecorationsProperty)
        btnUnderline.IsChecked = (temp IsNot DependencyProperty.UnsetValue) _
        AndAlso (temp.Equals(TextDecorations.Underline))
 
        temp = rtbEditor.Selection.GetPropertyValue(Inline.FontFamilyProperty)
        cmbFontFamily.SelectedItem = temp
        temp = rtbEditor.Selection.GetPropertyValue(Inline.FontSizeProperty)
        cmbFontSize.Text = temp.ToString()
 
 
 
    End Sub
 
    Private Sub Open_Executed(sender As Object, e As ExecutedRoutedEventArgs)
 
        Dim dlg As New OpenFileDialog()
        dlg.Filter = "Rich Text Format (*.rtf)|*.rtf|All files (*.*)|*.*"
        If dlg.ShowDialog() = True Then
            Dim fileStream As New FileStream(dlg.FileName, FileMode.Open)
            Dim range As New TextRange(rtbEditor.Document.ContentStart, _
              rtbEditor.Document.ContentEnd)
            range.Load(fileStream, DataFormats.Rtf)
        End If
 
    End Sub
 
    Private Sub Save_Executed(sender As Object, e As ExecutedRoutedEventArgs)
        Dim dlg As New SaveFileDialog()
        dlg.Filter = "Rich Text Format (*.rtf)|*.rtf|All files (*.*)|*.*"
        If dlg.ShowDialog() = True Then
            Dim fileStream As New FileStream(dlg.FileName, FileMode.Create)
            Dim range As New TextRange(rtbEditor.Document.ContentStart, _
              rtbEditor.Document.ContentEnd)
            range.Save(fileStream, DataFormats.Rtf)
        End If
    End Sub
 
    Private Sub cmbFontFamily_SelectionChanged(sender As Object, e As _
      SelectionChangedEventArgs)
        If cmbFontFamily.SelectedItem IsNot Nothing Then
            rtbEditor.Selection.ApplyPropertyValue(Inline.FontFamilyProperty, _
              cmbFontFamily.SelectedItem)
        End If
    End Sub
 
    Private Sub cmbFontSize_TextChanged(sender As Object, e As _
      TextChangedEventArgs)
        rtbEditor.Selection.ApplyPropertyValue(Inline.FontSizeProperty, _
        cmbFontSize.Text)
    End Sub
 
End Class