detecting emails inside an http header

Question

i am building up a proxy in csharp and one of my tasks is to find emails inside an http header, problem is that inside the data that i get i receive %40 instead of @, could anyone please tell me how can i detect emails when the @ inside the mail address is being replaced with %40? here is my code for getting email addresses inside a given string (with @ and not %40 instead) Code :

  string regexPattern = @"[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}";
  Regex regex = new Regex(regexPattern);
  MatchCollection matches = regex.Matches(this._context.Request.Headers[i]);
  foreach (Match match in regex.Matches(this._context.Request.Headers[i]))
  {// any email address should be printed 
         Console.WriteLine(match.Value);
  }

Answer 1

Not sure if I understood your question. Why don't you just replace @ with %40 in regex you provided? So:

string regexPattern = @"[A-Za-z0-9._%-]+%40[A-Za-z0-9.-]+\.[A-Za-z]{2,4}";

Answer 2

URL decode your data before running it through the regex:

regex.Matches(this._context.Server.UrlDecode(this._context.Request.Headers[i]))

Or:

regex.Matches(HttpUtility.UrlDecode(this._context.Request.Headers[i]))

Answer 3

Use OR (|) to allow @ or "%40"

[A-Za-z0-9._%-]+(@|%40)[A-Za-z0-9.-]+.[A-Za-z]{2,4}