title: Using custom objects in a view model Knockout
body: <p>I am coming from Silverlight to Knockout.js. When I would create ViewModels in Silverlight, I would often times have something like this:</p>
  
  <pre><code>public class MyViewModel : ViewModel
  {
    private MyCustomClass custom = null;
    public MyCustomClass Custom
    {
      get { return custom; }
      set { custom = value;
        NotifyPropertyChanged("MyCustomClass");
      }
    }
  }
  
  &lt;TextBox Text="{Binding Path=Custom.PropertyName, Mode=TwoWay}" /&gt;
  </code></pre>
  
  <p>However, I'm not sure how to do the same kind of thing in Knockout.js. Currently, I have:</p>
  
  <pre><code>&lt;input type="text" data-bind="value:propertyName" /&gt;
  
  var viewModel = {
    custom: {
      propertyName:""
    }
  }
  </code></pre>