Replacing a string with strings that include parenthesis issue

Question

i am currenty having a problem related with regex.replace . I have an item in checkedlistbox that contains a string with parenthesis "()" :

regx2[4] = new Regex( "->" + checkedListBox1.SelectedItem.ToString());

the example setence inside the selected item is

hello how are you (today)

i use it in regex like this :

if (e.NewValue == CheckState.Checked)
{
    //replaces the string without parenthesis with the one with parenthesis
    //ex:<reason1> ----> hello, how are you (today) (worked fine)
    richTextBox1.Text = regx2[selected].Replace(richTextBox1.Text,"->"+checkedListBox1.Items[selected].ToString());
}
else if (e.NewValue == CheckState.Unchecked)
{
    //replaces the string with parenthesis with the one without parenthesis
    //hello, how are you (today)----><reason1> (problem)
    richTextBox1.Text = regx2[4].Replace(richTextBox1.Text, "<reason" + (selected + 1).ToString() + ">");
}

it is able to replace the string on the first condition but unable to re-replace the setences again on second because it has parenthesis "()", do you know how to solve this problem?? thx for the response :)

Answer 1

Instead of:

regx2[4] = new Regex( "->" + checkedListBox1.SelectedItem.ToString());

Try:

regx2[4] = new Regex(Regex.Escape("->" + checkedListBox1.SelectedItem));

Answer 2

To use any of the special characters as a literal in a regex, you need to escape them with a backslash. If you want to match 1+1=2, the correct regex is 1\+1=2. Otherwise, the plus sign has a special meaning.

http://www.regular-expressions.info/characters.html

special characters:

• backslash \,
• caret ^,
• dollar sign $,
• period or dot .,
• vertical bar or pipe symbol |,
• question mark ?,
• asterisk or star *,
• plus sign +,
• opening parenthesis (,
• closing parenthesis ),
• opening square bracket [,
• opening curly brace {

To fix it you could probably do this:

regx2[4] = new Regex("->" + checkedListBox1.SelectedItem.ToString().Replace("(", @"\(").Replace(")", @"\)"));

But I would just use string.replace() since you aren't doing any parsing. I can't tell what you're transforming from/to and why you use selected as an index on the regex array in the if and 4 as the index in the else.