title: Regex to allow only numbers not alphanumeric , letters and negative asp.net mvc
body: <p>hey everyone i want to know that i want to match regex only positive integers and dont allow alphanumeric letters and negative integer. 
  i am using this ajax but it's not work as expected what should i do please help me</p>
  
  <pre><code>[RegularExpression(@"[0-9]+$", ErrorMessage = "Invalid Format")]
  public int? estddays { get; set; }
  </code></pre>