使用Regex.Replace（）替换单词列表失败

Question

I am trying to replace words in a long string with some HTML-tags. I seem to miss something when trying to do this for multiple words from a List, it does however work nicely for single Words.

Here is what i tried: For testing purposes i reduced and altered the string to this:

string strTest = "Ein toller Testtext mit Folge und Folgen sowie Folgen<p> und <p>Folge und Cauchyfolgen und Cauchy-Folgen und Folgeerscheinungen und Folgendem";

The following code was used as a text to replace "Folge" with "WOW":

strResult = Regex.Replace(strTest, "\\b" + "Folge" + "\\b", "WOW");

This resulted in: "Ein toller Testtext mit WOW und Folgen sowie Folgen<p> und <p>WOW und Cauchyfolgen und Cauchy-Folgen und Folgeerscheinungen und Folgendem" , which is the desired result for a single word.

The following code resulted in the same, but is using my list of Objects, where "strWort" is the word i want to replace. Note the Value of listTooltips[39].strWort is "Folge".

strResult = Regex.Replace(strTest, "\\b" + listTooltips[39].strWort + "\\b", "WOW");

In the next step i tried to do this for the whole list. So i did the following:

for (int i = 0; i < listTooltips.Count(); i++)
{
    strResult = Regex.Replace(strTest, "\\b" + listTooltips[i].strWort + "\\b", "WOW");
}

The result is an unchanged String. And i am lost as to why. As noted it does work if i only put one Word to replace, even if i use a specific object from my list. So i am quite sure the code for the list is not wrong, at least not completly.

Additional things i tried:

• putting the value of each word into a seperate string and using that for the Regex.Replace. Failed.
• using a MessageBox.Show() to display the value of listTooltips[i].strWort to make sure, everything outputting as expected.
• using Regex.Match to check if the above code actually finds anything and yes, it does find everything. It just does not replace ist for some reason.
• not using Regex and going the string.replace-method instead. This is working with the above loop, but is causing differend unwanted results due to missing a filter / matchmode. ie "Folgen" is getting replaced to "WOWn" ect.

Really wondering WHY this is behaing as it does mainly, to better understand it. But id love a solution as well of corse :-)

Thanks in advance!

Answer 1

In your for loop, you're always performing a Regex.Replace() on the original text strTest .

You need to call it on the previously-replaced text in strResult , otherwise each replacement (except for the very last one) will be overwritten with the original text.

Try this:

string strResult = strTest;
for (int i = 0; i < listTooltips.Count(); i++) {
    strResult = Regex.Replace(strResult , "\\b" + listTooltips[i].strWort + "\\b", "WOW");
}