Demo - ComboBox

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdn.grapecity.com/wijmo/5.latest/styles/wijmo.min.css">
<script src="https://cdn.grapecity.com/wijmo/5.latest/controls/wijmo.min.js"></script>
<script src="https://cdn.grapecity.com/wijmo/5.latest/controls/wijmo.input.min.js"></script>
<script src="https://cdn.grapecity.com/wijmo/5.latest/controls/wijmo.grid.min.js"></script>
<link rel="stylesheet" href="https://code.jquery.com/ui/1.11.4/themes/black-tie/jquery-ui.css">
<script src="https://code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<div class="container">
  
  <h3>
    ComboBox not displaying menu dropdown properly in Dialog
  </h3>
    
    <button id="dialogButton" type="button" onclick="openDialog()">
    Open Dialog
    </button>
    <dialog id="comboDialog">
        <div>
          Input controls in a dialog
        </div>
        <div id="theComboBox"></div>
        <div id="theAutoComplete"></div>
        <div id="theDateTime"></div>
        <div id="theDate"></div>
        
      <button type="button" id="cancel" onclick="closeDialog()">
        Cancel
      </button>
      
    </dialog>
    
  </div>

CSS

label {
  width: 150px;
  text-align: right;
}
label + div {
  display: inline-block;
  max-width: 160px;
  white-space: pre;
  overflow: hidden;
  text-overflow: ellipsis;
}

body {
  margin-bottom: 36pt;
}

JavaScript

function openDialog() {
  $('#comboDialog').dialog();
}

onload = function() {

	// data used in the combo
	var theData = [
  	{ name: 'Zero', value: 0 },
  	{ name: 'Low', value: 10 },
  	{ name: 'Medium', value: 50 },
  	{ name: 'High', value: 100 },
  	{ name: 'Maximum', value: 150 },
  ];

  
  // create the combo
  var theComboBox = new wijmo.input.ComboBox('#theComboBox', {
    displayMemberPath: 'name',
    selectedValuePath: 'value',
  	itemsSource: theData
  });
  var theAutoComplete = new wijmo.input.ComboBox('#theAutoComplete', {
    displayMemberPath: 'name',
    selectedValuePath: 'value',
  	itemsSource: theData
  });
  
  var dateTime = new wijmo.input.InputDateTime('#theDateTime');
  
  var date = new wijmo.input.InputDate('#theDate');
}