Replace a character only in the start of a string

Question

I want to replace a character ":" with a space " " character only in the beginning of a string, if the ":" character is present in the beginning. The TrimStart(":".ToCharArray()) removes the character not replaces it. And Replace(":", " ") replaces all the occurrences of the character even if they are not in start. What is the solution? Can Regex be used for it? Or any other way? The desired result is:

:abc -> abc
abc  -> abc
a:bc -> a:bc
abc: -> abc:

Answer 1

You can use this regular expression:

var output = Regex.Replace(input, "^:", " ");

But for something this simple, I'd recommend using conventional string methods:

var output = 
    (!string.IsNullOrEmpty(input) && input[0] == ':') 
    ? " " + input.Substring(1) : input;

Note: the check for null or empty strings may not be necessary in your case.