Word VSTO 加载项：通过其范围更改段落的文本

Question

I'm programming an add-in which uses a GroupContentControl (GCC) to write-protect each paragraph that uses the "Heading 1" style. Once protected, those headings can only be changed through the add-in. To that end, I wrote a simple method that removes the paragraph's GCC, assigns a new value to the paragraph's Range.Text property, sets the style to Heading 1 again, and then sets a new GCC to protect the paragraph.

I'm still new to Office programming, and my assumption was that the Range object could be used throughout the whole process. However, the method misbehaves : it inserts a carriage return after the new paragraph text, and then takes the next paragraph in the document and makes it a Heading 1 paragraph, then write-protects it.

Here's my method, along with calls to a logging function to see how the Range evolves :

void ChangeParagraphText (Word.Paragraph p, string NewText)
{
    Log("Range 1 : " + p.Range.Start + " - " + p.Range.End);
    UnlockTitle(p);     // remove the paragraph's GroupContentControl     
    Log("Range 2 : " + p.Range.Start + " - " + p.Range.End);
    p.Range.Text = NewText;   // change the paragraph's text
    Log("Range 3 : " + p.Range.Start + " - " + p.Range.End);
    p.Range.set_Style(Globals.ThisAddIn.Application.ActiveDocument.Styles[Word.WdBuiltinStyle.wdStyleHeading1]);
    Log("Range 4 : " + p.Range.Start + " - " + p.Range.End);
    LockTitle(p);       // write-protect the paragraph with a GroupContentControl
    Log("Range 5 : " + p.Range.Start + " - " + p.Range.End);
}

Once it has run, here are the contents of the log file :

Range 1 : 90 - 99
Range 2 : 90 - 97
Range 3 : 100 - 102
Range 4 : 100 - 102
Range 5 : 100 - 104

This taught me some interesting things. For starters, the length of the Range decreases by two after removing the GCC, and increases by two when adding a GCC. The important part, though, is the third log entry : it shows that as soon as I assign the paragraph's Range.Text, the Range changes completely. The values match the next paragraph in my test document.

Reading the Range.Text property also shows that it ends with a line feed character (ASCII 13). If I omit it, I end up with the next paragraph appended to my Heading 1 paragraph. If I put it in, I end up with the second paragraph being treated as the Heading 1 paragraph. None of those behaviors works for me.

My question is : how do I programmatically change the text of a paragraph ? I assume it has to be possible, but if it's not, what's the workaround ? I've been thinking of creating a new paragraph after the one I want to change, and then deleting the old one, but that seems inelegant.

Answer 1

First, quick answer to your stated question: how to replace the text of the paragraph while leaving the paragraph, itself, intact. I'm not able to use the code you provide as it doesn't show how you derive p . So I'm taking an arbitrary Paragraph object:

Word.Range rngPara = doc.Paragraphs[1].Range;
object unitCharacter = Word.WdUnits.wdCharacter;
object backOne = -1;
rngPara.MoveEnd(ref unitCharacter, ref backOne);
rngPara.Text = "replacement text";

Background information :

The most important aspect of your problem is understanding Word Range objects.

First, never rely on the Start and End properties for identifying a Range. They're OK for "snapshots", or dynamically setting one Range's Start or End point to that of a second. But as soon as any editing whatsoever takes place in a document, you can throw them away.

When you need to work with Ranges, use Range objects (variables) for the duration of the running code.

Yes, as you analyze, Paragraph.Range.Text does include the end-of-paragraph mark. This is ANSI 13 and is not just a carriage return; under the covers it stores a load of information about the paragraph formatting. When you want to work with only the text, shorten the Range back by one character to leave the paragraph mark out of the Range. This can be done using the MoveEnd method.