title: check alphanumeric characters in string in c#
body: <p>I have used the following code but it is returning false though it should return true    </p>
  
  <pre><code>string check,zipcode;
  zipcode="10001 New York, NY";
  check=isalphanumeric(zipcode)
  
  public static Boolean isAlphaNumeric(string strToCheck)
  {
      Regex rg = new Regex("[^a-zA-Z0-9]");
  
      //if has non AlpahNumeric char, return false, else return true.
      return rg.IsMatch(strToCheck) == true ? false : true;
  }
  </code></pre>