title: Starting DataForm in edit mode
body: <p>DataFrom works fine with AutoGenerateFields and no styles, but when I add a textbox style to the DataFormTextField's EditingElementStyle like this </p>
  
  <pre><code>Style x:Key="FieldTextBoxStyle" TargetType="TextBox"&gt;
      &lt;Setter Property="Template"&gt;
          &lt;Setter.Value&gt;
              &lt;ControlTemplate TargetType="TextBox"&gt;
                  &lt;Grid x:Name="RootElement"&gt;
                                &lt;Grid.Resources&gt;
                                      &lt;Storyboard x:Key="Normal State"/&gt;
                                      &lt;Storyboard x:Key="Focused State"/&gt;
                                  &lt;/Grid.Resources&gt;
                                  &lt;ScrollViewer x:Name="ContentElement"  Background="Transparent" Padding="{TemplateBinding Padding}" Margin="1,1,1,1"&gt;
  
                                  &lt;/ScrollViewer&gt;
  
                  &lt;/Grid&gt;
              &lt;/ControlTemplate&gt;
          &lt;/Setter.Value&gt;
      &lt;/Setter&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>and this </p>
  
  <pre><code>DataForm dForm = new DataForm() { AutoGenerateFields = false, AutoEdit = true, AutoCommit = true, CommandButtonsVisibility = DataFormCommandButtonsVisibility.None, Foreground = new SolidColorBrush(Colors.Black), Header = "Basic Infomation" };
  
  dForm.Fields.Add(new DataFormTextField() { FieldLabelContent = "Company Name", Binding = new Binding("Name"), EditingElementStyle = Resources["FieldTextBoxStyle"] as Style });
  </code></pre>
  
  <p>I want the form to start in Edit mode without having to click a button. But since Name is required</p>
  
  <pre><code>[Required]
  </code></pre>
  
  <p>public string Name;</p>
  
  <p>The Binding triggers an error because Name is empty by default... Is my styling wrong?</p>