Question

Rather than describing what I want (it’s difficult to explain), Let me provide an example of what I need to accomplish in C# using a regular expression:

"HelloWorld" should be transformed to "Hello World" 
"HelloWORld" should be transformed to "Hello WO Rld" //Two consecutive letters in capital should be treatead as one word
"helloworld" should be transformed to "helloworld"

EDIT:

"HellOWORLd" should be transformed to "Hell OW OR Ld"

Every 2-consecutive capital letters should be considered one word.

Is this possible?

Answer 1

This is fully working C# code, not just the regex:

Console.WriteLine(
    Regex.Replace(
        "HelloWORld", 
        "(?<!^)(?<wordstart>[A-Z]{1,2})", 
        " ${wordstart}", RegexOptions.Compiled));

And it prints:

Hello WO Rld

Update

To make this more UNICODE/international aware, consider replacing [A-Z] by \p{Lt} (meaning a UNICODE code point that represents a Letter in uppercase). The result for the current input would the same. So here is a slightly more compelling example:

Console.WriteLine(Regex.Replace(
            @"ÉclaireürfØÑJßå",
            @"(?<!^)(?<wordstart>\p{Lu}{1,2})", 
            @" ${wordstart}",
            RegexOptions.Compiled));