Question

What I’m trying to do is open up a file and search for “searchText”. I want to replace all the instances of it in the file with a new link, which is actually just the filename with an achor link so instead of opening up javascript it just goes to another point in the page.

So far what I have is this:

private void writeNotes(){
        StreamReader reader = new StreamReader(openFileDialog1.FileName);
        string content = reader.ReadToEnd();

        reader.Close();

        string fileName = openFileDialog1.SafeFileName;
        string searchText = "<a class=\"x-fn\" href=\"javascript:void(0);\">";
        string replaceText = "<a class=\"x-fn\" href=\"" + fileName + "#fn" + "\">";

        content = Regex.Replace(content, searchText, replaceText);

        StreamWriter writer = new StreamWriter(openFileDialog1.FileName);
        writer.Write(content);
        writer.Close();

However, after writing and closing… I open up the file and no changes were made. Besides that, what I want to do is add a number that counts up after “#fn” for every instance of replacement. So, basically, for every time I replace the javascript link with another, I want it to be:

<a class="x-fn" href="fileName#fn1">

And then when I replace the second instance of javascript, it reads

<a class="x-fn" href="fileName#fn2">

and so on…

I imagine I would have to count the instances of how many times the javascript appears, replace it, and use a for loop to iterate throughout all of the new links and add the #fn(n) at the end?

Answer 1

Your problem is that you have metacharacters (in this case, the open and close paren in “void(0)”). Instead of representing literal open and close parens, that is creating a regular expression group, which is causing your match to fail. If you escape the parens with a backslash, it will work as expected.

However, since you’re just matching a string literal, you don’t need to use regular expressions at all; it’ll be faster to use string.Replace.

As for the second part of your question, that’s a little trickier. There’s no easy way to do it that I know of, so the best approach is to look for your search text in the input, and then build up a StringBuilder as you go along, incrementing a count variable. In the following example, the word “the” is replaced by “(0)” and “(1)” for simplicity’s sake, but you can adapt it to your problem easily enough.

var content = "the quick brown fox jumped over the lazy dog";
var searchText = "the";
var sb = new StringBuilder();
var idx = -1; // will hold the index of our search text
var uncopiedIdx = 0; // the start index of what hasn't been copied yet
var replacementCount = 0;
while( (idx = content.IndexOf( searchText, idx+1 )) != -1 ) {
    // copy everything leading up to our search text
    sb.Append( content.Substring( uncopiedIdx, idx-uncopiedIdx ) );
    // copy the replacement text, with the replacement count
    var replacement = "(" + replacementCount++ + ")";
    sb.Append( replacement );
    // skip over the search text
    uncopiedIdx = idx + searchText.Length;
}
// copy everything after the last match
sb.Append( content.Substring( uncopiedIdx ) );