文本下划线检测会导致错误 - 为什么？

Question

我按照本教程创建了一个富文本编辑器：How-to: Creating a Rich Text Editor

粗体和斜体按预期工作，但下划线会引发错误。我不明白为什么，希望有人对此有所了解！

工具栏和 RichTextBox 中的切换按钮：

<ToolBar>
    <ToggleButton Command="EditingCommands.ToggleBold" Name="btnBold" Height="25" Width="20" HorizontalAlignment="Left" Content="F" FontWeight="ExtraBold"/>
    <ToggleButton Command="EditingCommands.ToggleItalic" Name="btnItalic" Height="25" Width="20" HorizontalAlignment="Left" Content="K" FontStyle="Oblique"/>
    <ToggleButton Visibility="Hidden" Command="EditingCommands.ToggleUnderline" Name="btnUnderline" Height="25" Width="20" HorizontalAlignment="Left">
        <ToggleButton.Content>
            <TextBlock TextDecorations="Underline" Text="U"/>
        </ToggleButton.Content>
    </ToggleButton>
    <ComboBox Name="cmbFontSize" Height="20" Width="50" IsEditable="True" TextBoxBase.TextChanged="cmbFontSize_TextChanged" />
</ToolBar>
<RichTextBox Name="rtbEditor" SelectionChanged="rtbEditor_SelectionChanged"/>

子使用按钮：

Public Sub rtbEditor_SelectionChanged(sender As Object, e As RoutedEventArgs)
    Dim temp As Object = rtbEditor.Selection.GetPropertyValue(Inline.FontWeightProperty)
    btnBold.IsChecked = (temp <> Nothing) AndAlso (temp.Equals(FontWeights.Bold))
    temp = rtbEditor.Selection.GetPropertyValue(Inline.FontStyleProperty)
    btnItalic.IsChecked = (temp <> Nothing) AndAlso (temp.Equals(FontStyles.Italic))
    temp = rtbEditor.Selection.GetPropertyValue(Inline.TextDecorationsProperty)
    btnUnderline.IsChecked = (temp <> DependencyProperty.UnsetValue) AndAlso (temp.Equals(TextDecorations.Underline))

    temp = rtbEditor.Selection.GetPropertyValue(Inline.FontSizeProperty)
    cmbFontSize.Text = temp.ToString()
End Sub

这会引发错误：

btnUnderline.IsChecked = (temp <> DependencyProperty.UnsetValue) AndAlso (temp.Equals(TextDecorations.Underline))

错误消息（翻译自瑞典语）：

operator <> not defined for type TextDecorationCollection and NamedObject

为什么？？

Answer 1

使用：

if blubb isNot nothing
End if

而不是：

if blubb <> nothing
End if

您的代码：

Public Sub rtbEditor_SelectionChanged(sender As Object, e As RoutedEventArgs)

Dim temp As Object = rtbEditor.Selection.GetPropertyValue(Inline.FontWeightProperty)
btnBold.IsChecked = (temp isNot Nothing) AndAlso (temp.Equals(FontWeights.Bold))
temp = rtbEditor.Selection.GetPropertyValue(Inline.FontStyleProperty)
btnItalic.IsChecked = (temp isNot Nothing) 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.FontSizeProperty)
cmbFontSize.Text = temp.ToString()

End Sub

文本下划线检测会导致错误 - 为什么？

Text underline detection causes an error - why?

wpf

vb.net

runtime-error

text-decorations