[sp{L}]

string tmp = "foo";
var match = tmp.IndexOfAny("0123456789".ToCharArray()) != -1;

if ( !Regex.Match ( stringToCheck, "^[0-9]+$" ).Success ) {
      // TODO.
  }

var regex = new Regex(@"[0-9]", RegexOptions.IgnoreCase);
var m = regex.Match(stringValue);
if (m.Success)
    //TODO