How do you do case-insensitive string replacement using regular expressions?

Question

I know precisely zilch about regular expressions and figured this was as good an opportunity as any to learn at least the most basic of basics.

How do I do this case-insensitive string replacement in C# using a regular expression?

myString.Replace("/kg", "").Replace("/KG", "");

(Note that the '/' is a literal.)

Answer 1

You can use:

myString = Regex.Replace(myString, "/kg", "", RegexOptions.IgnoreCase);

If you're going to do this a lot of times, you could do:

// You can reuse this object
Regex regex = new Regex("/kg", RegexOptions.IgnoreCase);
myString = regex.Replace(myString, "");

Using (?i:/kg) would make just that bit of a larger regular expression case insensitive - personally I prefer to use RegexOptions to make an option affect the whole pattern.

MSDN has pretty reasonable documentation of .NET regular expressions.

Answer 2

It depends what you want to achieve. I assume you want to remove a sequence of characters after a slash?

string replaced = Regex.Replace(input,"/[a-zA-Z]+","");

or

string replaced = Regex.Replace(input,"/[a-z]+","",RegexOptions.IgnoreCase);

Answer 3

"/[kK][gG]" or "(?i:/kg)" will match for you.

declare a new regex object, passing in one of those as your contents. Then run regex.replace.

Answer 4

    Regex regex = new Regex(@"/kg", RegexOptions.IgnoreCase );
    regex.Replace(input, "");

Answer 5

Like this:

myString = Regex.Replace(myString, "/[Kk][Gg]", String.Empty);

Note that it will also handle the combinations /kG and /Kg, so it does more than your string replacement example.

If you only want to handle the specific combinations /kg and /KG:

myString = Regex.Replace(myString, "/(?:kg|KG)", String.Empty);

Answer 6

Here is an example using the Regex.replace function.