How to match the first occurrence of a character and split it

Question

I have a text file from which I want to store Keys and Values in a String array.

In this case, Key is something like &

Answer 1

Using regular expression captures

private static Regex _regex = new Regex(@"^([\p{L}_ ]+):?(.+)$");

....

Match match = _regex.Match(line);
if (match.Success)
{
    string key = match.Groups[1].Captures[0].Value;
    string value = match.Groups[2].Captures[0].Value;
}

The regexp is a static member to avoid compiling it for every usage. The ? in the expression is to force lazy behavior (greedy is the default) and match the first :.

Link to Fiddle.

Edit

I've updated the code and fiddle after your comment. I think this is what you mean:

Key: Any letter, underscore and whitespace combination (no digits) Value: anything Separator between key and value: :