title: ng-change not working with dropdown list
body: <p>In the code <code>ng-change</code> is not working it gives an error. Why? I need to execute the method <code>show()</code> every time the selected value changes. Also the below <code>div</code> tag should be visible only after selection of a valid list value.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code> &lt;div class="form-group"&gt;
   &lt;label&gt;SOURCE&lt;/label&gt;
   &lt;select class="form-control" name="ddlFirst" ngmodel="ddlSource" ng-change="show()"&gt;
   &lt;option value="null" ng-selected="true"&gt;--Select Sprint--&lt;/option&gt;
   &lt;option  ng-repeat="s in AllS" value="{{s.Id}}"&gt;{{s.Name}}&lt;/option&gt;
   &lt;/select&gt;
   &lt;/div&gt;
  
  //this div should be visible only when a valid list value is selected.s.id will hv +ve value on valid list value selection
  
  &lt;div ng-show="ddlSource==isNumber()"&gt;
   &lt;label&gt; hiiiiii&lt;/label&gt;
  &lt;/div&gt;
  
  
  result is:
  
  Error: [$compile:ctreq] Controller 'ngModel', required by directive 'ngChange', can't be found!
  http://errors.angularjs.org/1.3.15/$compile/ctreq?p0=ngModel&amp;p1=ngChange
      at REGEX_STRING_REGEXP (angular.js:64)
      at getControllers (angular.js:7584)
      at nodeLinkFn (angular.js:7773)
      at compositeLinkFn (angular.js:7118)
      at compositeLinkFn (angular.js:7121)
      at nodeLinkFn (angular.js:7764)
      at compositeLinkFn (angular.js:7118)
      at compositeLinkFn (angular.js:7121)
      at compositeLinkFn (angular.js:7121)
      at compositeLinkFn (angular.js:7121)</code></pre>
  </div>
  </div>
  </p>