title: What is the correct regular expression for a letter x between a number
body: <p>Just want to ask a question regarding regular expression.. I want to find any x between a number, like 7 x 3 or 7x3 where 7 and 3 is any number. I'm not really in regexpression. so far  this my code; What is the correct regular expression here for the 7 x 3 or 7x3</p>
  
  <pre><code>public void CheckMultiplicationEntity()
      {
          int lineno = 0;
          bool start = false;
          foreach (string line in _contentList)
          {
              lineno++;
              if (line.Contains("&lt;text&gt;"))
              {
                  start = true;
              }
              if (start)
              {
                  foreach (Match match in Regex.Matches(line, @"([0-9]x[0-9]|[0-9]\s*x\s*[0-9]"))
                  {
                      List&lt;ErrorModel&gt; errorlist = ErrorList;
                      ErrorModel errorModel = new ErrorModel()
                      {
                          LineNumber = lineno,
                          ErrorMessage = "Please check \"x\" should &amp;#x00D7;",
                          Text = ShortenText(match.Value)
                      };
                      errorlist.Add(errorModel);
                  }
              }
          }
  </code></pre>