title: RaisePropertyChanged for Property of an Object
body: <p>i have a model user:</p>
  
  <pre><code>public class User
  {
      public string Name { get; set; }
      public int Level { get; set; }
  }
  </code></pre>
  
  <p>in the view:</p>
  
  <pre><code>&lt;TextBox Text="{Binding NewUser.Name}"/&gt;
  &lt;TextBox Text="{Binding NewUser.Level}"/&gt;
  </code></pre>
  
  <p>and the property in the VM:</p>
  
  <pre><code>public User NewUser
      {
          get { return _newUser; }
          set
          {
              if (_newUser == value)
                  return;
              _newUser = value;
              RaisePropertyChanged("NewUser");
          }
      }
  </code></pre>
  
  <p>this code does update the property:
  <code>NewUser = new User() { Name = "test", Level = 1 };</code></p>
  
  <p>this code does not:
  <code>NewUser.Name = "test";</code></p>
  
  <p>what am i doing wrong? i'm using mvvm light.</p>