Require all characters of a range [duplicate] - regex

Question

I need a Regex to match any word that contains letters: m+a+h+d together in any order
so, Mohamed, Hamada and Mahmoud matches, but hammer don't match
I tried do the following (I'm new to the Regex!):
Regex reg=new Regex("[mahd]");
But obviously it is not the correct pattern

Answer 1

When you want to match some substrings in any order, you either use alternation where all possible variations are enumerated, or use anchored lookaheads.
In this case, I'd suggest using positive lookaheads that will ensure both free order of the letters in a word and their obligatory presence in the word matched.
Use
(?i)\b(?=\w*m)(?=\w*a)(?=\w*h)(?=\w*d)\w+
See the regex demo (NOTE: You may replace \w with \p{L} to only match letters).
Details:
(?i) - case insensitive mode on
\b - a leading word boundary
(?=\w*m) - after 0+ word chars (i.e. letters, digits or underscores), there must be m
(?=\w*a) - after 0+ word chars, there must be a
(?=\w*h) - after 0+ word chars, there must be h
(?=\w*d) - after 0+ word chars, there must be d
\w+ - 1 or more letters, digits or underscores (you may replace with \p{L} to only match letters).
C# demo:
var str = "Mohamed, Hamada and Mahmoud match, but not hammer";
var letters = "mahd";
var pat = string.Format(#"\b{0}\w+\b", string.Join("", letters.Select(s => string.Format(#"(?=\w*{0})", s))));
var result = Regex.Matches(str, pat, RegexOptions.IgnoreCase)
.Cast<Match>()
.Select(match => match.Value)
.ToList();
Console.WriteLine(String.Join("\n", result)); // Demo line