在RichTextBox开头插入文本以保持颜色不变

// 获取RichTextBox的当前文本内容和格式
TextRange originalContent = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
string originalText = originalContent.Text;
TextPointer originalPosition = richTextBox.CaretPosition;

// 在要插入的文本前面创建一个新的段落，并设置格式
Paragraph newParagraph = new Paragraph();
newParagraph.Foreground = originalContent.GetPropertyValue(TextElement.ForegroundProperty);
newParagraph.FontFamily = originalContent.GetPropertyValue(TextElement.FontFamilyProperty) as FontFamily;
newParagraph.FontSize = originalContent.GetPropertyValue(TextElement.FontSizeProperty) as double?;

// 将要插入的文本添加到新段落的文本内容中
Run newRun = new Run("要插入的文本");
newParagraph.Inlines.Add(newRun);

// 将新段落插入到RichTextBox的开头位置
richTextBox.Document.Blocks.InsertBefore(originalContent.Start.Paragraph, newParagraph);

// 恢复原始的文本内容和光标位置
richTextBox.Document.Blocks.Remove(originalContent.Start.Paragraph);
richTextBox.Document.Blocks.Add(originalContent.Start.Paragraph);
richTextBox.CaretPosition = originalPosition;