c# - Check if string is valid represantion of HEX number

Question

I am total noob regarding regex. My goal is to check wether a string is a valid represantion of a HEX number. Currently my implementation (which I find really un-efficient) is having a List with all HEX digits (0,1,...9,A,B..F) and check wether my string contains chars not contained in given List. I bet this can be easily done using regular expressions but I have no Idea how to implement it.

 private bool ISValidHEX(string s)
       {
           List<string> ToCheck = new List<string>();
           for (int i = 0; i < 10; i++)
           {
               ToCheck.Add(i.ToString());
           }
           ToCheck.Add("A");
           ToCheck.Add("B");
           ToCheck.Add("C");
           ToCheck.Add("D");
           ToCheck.Add("E");
           ToCheck.Add("F");
           for (int i = 0; i < s.Length; i++)
           {
               if( !ToCheck.Contains(s.Substring(i,1)))
               {
                   return false;
               }
           }
           return true;
       }

Answer 1

I would have thought that it's quickest to attempt to convert your string to an integral type and deal with any exception. Use code like this:

int num = Int32.Parse(s, System.Globalization.NumberStyles.HexNumber);

The resulting code is possibly easier to follow than a regular expression and is particularly useful if you need the parsed value (else you could use Int32.TryParse which is adequately documented in other answers).

(One of my favourite quotations is by Jamie Zawinski: "Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems.")