Let me explain the actual problem I am facing.
When my SearchString is C+, the setup of regular expression below works fine. However when my searchstring is C++, it throws me an error stating --
parsing "C++" - Nested quantifier +.
Can anyone let me know how to get past this error?
RegExp = new Regex(Search_Str.Replace(" ", "|").Trim(), RegexOptions.IgnoreCase);
First of all, I believe that you'll learn much more by looking at some regex tutorials instead of asking here at your current stage.
To answer your question, I would like to point out that + is a quantifier in regexp, and means 1 or more times the previous character (or group), so that C+ will match at least 1 C, meaning C will match, CC will match, CCC will match and so on. Your search with C+ is actually matching only C!
C++ in a regex will give you an error, at least in C#. You won't with other regex flavours, including JGsoft, Java and PCRE (++ is a possessive quantifier in those flavours).
So, what to do? You need to escape the + character so that your search will look for the literal + character. One easy way is to add a backslash before the +: \+. Another way is to put the + in square brackets.
This said, you can use:
C\+\+
Or...
C[+][+]
To look for C++. Now, since you have twice the same character, you can use {n} (where n is the number of occurrences) to denote the number of occurrences of the last character, whence:
C\+{2}
Or...
C[+]{2}
Which should give the same results.
Plus + is a special symbol in regular expression. You must escape it.
Regex regex = new Regex(@"C+\+");
C+ means one or more C character (as in CCCC).I could not help but notice @ghost's answer is wrong.
This snippet is wrong:
Regex regex = new Regex(@"C+\+");
Because the first + is not escaped. So the meaning still is "one or more C characters followed by a plus sign". The correct form would be @"C\+\+"
