title: Text box validation for WP7
body: <p>Currently developing an application for Windows Phone that makes use of the bing maps geocode service. I have a search box where users can type in a location and then this is sent to bing maps which returns a geocoordinate.</p>
  
  <p>I have however, run into an issue with the search box. When I enter random letters no results are found and I have implemented code so the user is informed that there are no destinations found. The problem is though that if for whatever the reason the user decides to write some symbols eg: &amp;$%£" this crashes the application when bing maps returns some data.</p>
  
  <p>How would I go about validating the textbox entry so that it checks to see if there are any symbols in the string and then sends this off to the service if there are not? </p>
  
  <p>Any help is much appreciated!</p>