Question

What regular expression can I use for finding occurrences of uppercase followed by lowercase?

For example:

ABcDe

Here I would be hoping to find the ‘B’ and the ‘D’

Answer 1

You can use forward lookaheads. You haven’t said which “flavour” of regex you’re using, so here’s a C# example:

var regex = new Regex(@"[A-Z](?=[a-z])");
string str = "ABcDef";
regex.Replace(str, "?");
Console.WriteLine(str); // outputs "A?c?ef"

Additionally, for international characters, you can use Unicode character classes:

var regex = new Regex(@"\p{Lu}(?=\p{Ll})");