title: Rounded Corner TextBox in WPF
body: <p>i search the web for TextBox with rounded corners and find a xaml code like below:</p>
  
  <pre><code> &lt;Style TargetType="{x:Type my1:CustomTextBox}"&gt;
              &lt;Setter Property="HorizontalContentAlignment" Value="Center"/&gt;
              &lt;Setter Property="Template"&gt;
                  &lt;Setter.Value&gt;
                      &lt;ControlTemplate &gt;
                          &lt;Border Background="{TemplateBinding Background}" x:Name="Bd" 
  BorderThickness="2" CornerRadius="5" BorderBrush="#FFF9EAB6"&gt;
                              ***&lt;ScrollViewer x:Name="PART_ContentHost" /&gt;***
                          &lt;/Border&gt;
                          &lt;ControlTemplate.Triggers&gt;
                              &lt;Trigger Property="IsMouseOver" Value="True"&gt;
                                  &lt;Setter TargetName="Bd" Property="BorderBrush" Value="#FFC7B0B0"/&gt;
                              &lt;/Trigger&gt;
                              &lt;Trigger Property="IsKeyboardFocused" Value="True"&gt;
                                  &lt;Setter TargetName="Bd" Property="BorderBrush" Value="#FFC7B0B0"/&gt;
                                  &lt;Setter Property="Foreground" Value="Black"/&gt;
                              &lt;/Trigger&gt;
                              &lt;Trigger Property="IsKeyboardFocused" Value="False"&gt;
                                  &lt;Setter Property="Foreground" Value="#FFC7B0B0"/&gt;
                              &lt;/Trigger&gt;
                              &lt;Trigger Property="Width" Value="Auto"&gt;
                                  &lt;Setter Property="MinWidth" Value="120"/&gt;
                              &lt;/Trigger&gt;
                              &lt;Trigger Property="Height" Value="Auto"&gt;
                                  &lt;Setter Property="MinHeight" Value="27"/&gt;
                              &lt;/Trigger&gt;
                          &lt;/ControlTemplate.Triggers&gt;
                      &lt;/ControlTemplate&gt;
  
                  &lt;/Setter.Value&gt;
              &lt;/Setter&gt;
          &lt;/Style&gt;
  </code></pre>
  
  <p>i want to find out what is </p>
  
  <pre><code>&lt;ScrollViewer x:Name="PART_ContentHost" /&gt;
  </code></pre>
  
  <p>in detail and why not properly work my template if delete this line from it,
  please tell me completely in detail.</p>
  
  <p>thanks alot. </p>