Question

I need to apply paragraph formatting to a selection in a rich text box. My RTB will behave the same way as the rich text boxes on StackOverflow–the user can type text into the RTB, but they can also enter code blocks. The RTB will apply very simple formatting to the code block–it will change the font and apply a background color to the entire block, similar to what you see in the code block below.

Changing the font is pretty straightforward:

var textRange = new TextRange(rtb.Selection.Start, rtb.Selection.End);
textRange.ApplyPropertyValue(TextElement.FontFamilyProperty, "Consolas");
textRange.ApplyPropertyValue(TextElement.FontSizeProperty, 10D );

Now I need to apply some paragraph-level formatting. I need to set the paragraph margin to 0, so I don’t get a blank line between code lines, and I need to set the paragraph background color. Here’s my problem: I can’t figure out how to get the paragraph elements from the selection, so that I can apply formatting.

Any suggestions? An example of how to apply the Margin and Background properties would be incredibly helpful. Thanks!

Answer 1

Oh, that was easy.. Came across the answer with a little more research:

var textRange = new TextRange(TextBox.Selection.Start, TextBox.Selection.End);
textRange.ApplyPropertyValue(TextElement.FontFamilyProperty, "Consolas");
textRange.ApplyPropertyValue(TextElement.FontSizeProperty, 10D );
textRange.ApplyPropertyValue(Paragraph.MarginProperty, new Thickness(0));
textRange.ApplyPropertyValue(Paragraph.BackgroundProperty, "LightSteelBlue");

The only limitation is that the highlighting still extends only as far as the text, rather than to the right side of the control. I’ll leave this question open for a couple of days; if someone can tell me how to extend the background to the right edge of the control, I’ll accept your answer to this question.