(C#WPF)如何更改textrange背景颜色?

问题描述

我正在使用"flowdocumentreader"显示文本，"flowdocumentreader"的xaml代码很简单:

I am using a "flowdocumentreader" to show text, the xaml code of the "flowdocumentreader" is simple:

<FlowDocumentReader x:Name="myDocumentReader" ViewingMode="Scroll" VerticalAlignment="Stretch" ContextMenuOpening="myDocumentReader_ContextMenuOpening" Margin="0,0,0,0" Grid.Row="1" PreviewMouseDown="myDocumentReader_PreviewMouseDown">
    <FlowDocument x:Name="flow" LineHeight="{Binding ElementName=slider2, Path=Value}" PagePadding="{Binding ElementName=slider, Path=Value}">
        <Paragraph x:Name="paraBodyText"/>
    </FlowDocument>
</FlowDocumentReader>

我将.rtf文档加载到"flowdocumentreader"中，如下所示:

And I load .rtf documents to the "flowdocumentreader" like this:

paraBodyText.Inlines.Clear();
string temp = File.ReadAllText(dlg.FileName, Encoding.UTF8);
MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(temp));
TextRange textRange = new TextRange(flow.ContentStart, flow.ContentEnd);
textRange.Load(stream, DataFormats.Rtf);
myDocumentReader.Document = flow;

现在，我的问题是，如何在"flowdocumentreader"中获取字符串的背景色?

Now, my question is, how to get the background color of a string in the "flowdocumentreader"?

我知道如何搜索字符串，但不知道如何检查此类字符串的背景色.有没有办法做到这一点?我试图获取字符串的文本范围，然后执行以下操作:

I know how to search for a string, but I don't know how to check the back ground color of such string. Is there a way to do that? I tried to get the textrange of the string and then do this:

TextRange selection = ....; // this is the textrange of the string
var a = selection.GetPropertyValue(TextElement.BackgroundProperty)

但是，变量"a"始终返回null. :(

However, the variable "a" always returns null. :(

提前感谢您的时间.

编辑:我加载到"FlowDocumentReader"中的.rtf文档具有背景色.有些是绿色的，有些是黄色的.

EDIT:The .rtf document that I loaded into the "FlowDocumentReader" has background colors. Some are green and some are yellow.

推荐答案

如果您实际上设置了背景色怎么办?:

What if you actually set a background colour?:

TextRange selection = new TextRange(flow.ContentStart, flow.ContentEnd);
var a = selection.GetPropertyValue(TextElement.BackgroundProperty);
selection.ApplyPropertyValue(TextElement.BackgroundProperty, Brushes.Yellow);
a = selection.GetPropertyValue(TextElement.BackgroundProperty);

---

<FlowDocumentReader x:Name="myDocumentReader" ViewingMode="Scroll" VerticalAlignment="Stretch">
    <FlowDocument x:Name="flow">
        <Paragraph x:Name="paraBodyText">
            some text...
        </Paragraph>
    </FlowDocument>
</FlowDocumentReader>

TextRange的TextElement.BackgroundProperty属性没有默认值，这就是为什么您使用上述示例代码第一次从GetPropertyValue方法获得空引用的原因.

There is no default value for the TextElement.BackgroundProperty property of a TextRange which is why you get a null reference back from the GetPropertyValue method the first time using the above sample code.

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