title: Devextreme multiple selection List within a DropDownBox
body: <p>I'm trying to build a multiple selection dropdown list with DevExtreme jQuery. I have looked at the demos on the DevExpress Web site, they use a TreeView or a Grid inside a DropDownBox. Adapting that code, here is what I wrote:</p>
  
  <pre><code>$('#list1').dxDropDownBox({
  showClearButton: true,
  valueExpr: 'Value',
  displayExpr: 'Text',
  dataSource: new DevExpress.data.ArrayStore({
      data: source,
      key: 'Value'
  }),
  contentTemplate: function (e) {
      var value = e.component.option("Value"),
          $list = $("&lt;div&gt;").dxList({
              dataSource: e.component.option("dataSource"),
              valueExpr: 'Value',
              displayExpr: 'Text',
              showSelectionControls: true,
              selectionMode: "all",
              selectedItemKeys: value,
              onSelectionChanged: function (e) {
                  var selectedKeys = e.component.option("selectedItemKeys");
                  e.component.option("Value", selectedKeys);
              }
          });
  
      return $list;
  },
  </code></pre>
  
  <p>});</p>
  
  <p>The source is an array of objects with two properties (Text and Value are the same here, but they can sometimes be different):</p>
  
  <pre><code>[{"Text":"2000","Value":"2000"},{"Text":"2005","Value":"2005"}]
  </code></pre>
  
  <p>The list shows as it should, but I have two issues:</p>
  
  <ul>
  <li>When I select one or more items in the list, the texts of the selected items are not displayed in the dropdown box (in the demos, it is displayed as a comma-separated text).</li>
  <li>I have put the list1 element in an HTML form (not a DevExtreme form), and I don't know how to post the selected values with the form (or even get them in jQuery).</li>
  </ul>