WPF Flowdocument - Prevent line break before % sign

I've got a FlowDocument generating a document for a client, and it's getting a line break that they don't like. Is there any way to mark a section of text that it should avoid line breaks? Something like this:

<Paragraph>Here is a paragraph where there should be <span NoLineBreak=True>no line break</span> in a certain part.</Paragraph>

Obviously, a Span doesn't have a NoLineBreak property, but I'm wondering if there's some equivilant functionality available, or if someone can get me started on a way of implementing a SpanWithNoLineBreak class or RunWithNoLineBreak class?

UPDATE Actually, one issue I'm having is with a percent sign, where there isn't even a space:

<Paragraph>When I print and &#x00BD;% I want the one-half and '%' symbols to not line break between them.</Paragraph>

The & #x00BD; is the unicode for a ½ symbol. I'm getti开发者_如何学JAVAng a line wrap between the 1/2 and the % even though there's no space between them.

The Unicode character "Word Joiner" (U+2060) is intended for just this purpose. It "does not normally produce any space but prohibits a line break on either side of it" (Wikipedia). You place it between U+00BD and '%' to prevent a line break between them.

Unfortunately, WPF (or perhaps the typical fonts supplied with Windows) don't support it properly, and instead render it as a square box. As an alternative, you could use U+FEFF; the use of this character as a zero-width non-breaking space is now deprecated (it's reserved for use as a byte-order mark), but it worked as a line-break-preventer for me.

Finally, there are some other characters that can also be used for this purpose: U+202F (narrow no-break space) also prevents breaking, but also renders as a very thin space. U+00A0 (no-break space) prevents breaking and displays as a normal space.

Try replacing the spaces with non-breaking spaces.

EDIT: Well there's always the backup plan of just putting in TextBlocks in your FlowDocument with TextWrapping=NoWrap, but I'd try to find a better way...