Popup.AllowsTransparency Property

A Popup control can only contain transparent content when the application runs with full trust. An application that runs with full trust has complete access to system resources and is typically installed on the local system. For more information, seeSecurity (WPF).

This property cannot be set to true when the Popup is hosted in a XAML browser application (XBAP).

If the AllowsTransparency property is set to true in an application that does not run in full trust, the AllowsTransparency property value is changed to false. An application that is hosted in a browser is an example of an application that does not run in full trust.

The following example shows how to set the AllowsTransparency property on a Popup control.

myPopup.AllowsTransparency = true;

<DockPanel  Width="500" Background="Aqua">
  <Popup Placement="Center" PlacementRectangle="0,0,30,50"  
          IsOpen ="True" AllowsTransparency="True"
          PopupAnimation="Fade">
    <TextBlock Background="Purple">Popup Text</TextBlock>
  </Popup>
</DockPanel>

.NET Framework

.NET Framework Client Profile

• SecurityPermission 

  for setting this property to true. Associated enumeration: UnmanagedCode

Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

Reference